Disclaimer#1: I am not an audiophile and have not spent much time listening to equipment other than that which I have owned.
Disclaimer#2: Although the SR-680 is an A/V Dolby Digital receiver I am presently only using it as a STEREO Tuner/Preamp. It replaces my ailing NAD 7130 Receiver which was used in the same way.

Having said that, I find the SR-680 to be excellent. The receiver gives new life to my NAD 2400THX amp and Vandersteen 1B speakers. I was not prepared for such a dramatic difference. Compared to the 7130 the Marantz is cleaner, smoother, and considerably better focused. It is like removing a curtain from in front of my speakers. My system sounds more musical. Although the bass does not extend any deeper, and may even be slightly (very slightly) leaner, it is tighter and more convincing. The treble, in one word, is sweet. The glare is gone.

I was equally surprised about the FM tuner section. Despite having Signal/Noise specifications, 76/68 DB, mono/stereo respectively, that are inferior to my NAD, 80/75 DB, respectively. Listen seem to prove the contrary. Stations which I previously listened to in mono because of excessive hiss in stereo I can now listen to in stereo. In fact, I even enjoy listening to FM stereo which I never did before. Classical music is now very pleasant. FM sounds more like music than what I thought of as "FM".

I mentioned earlier that I do not use the Marantz's A/V features. I intend in the future, when I am willing to make the investment and committment, to expand. I am waiting to see what happens as more second generation DVD players it the market.
For those that are interested about the A/V features I will talk about what I have learned.

When I began looking for an A/V preamp I eventually got around to the Marantz AV-550. The only things that I was concerned about was replacing the NAD 7130 while improving the sound and that I probably wanted Dolby Pro Logic as well as Dolby Digital support built-in. (I did not want to add $600+ decoders later). I did not research A/V capabilities beyond the inclusion of two decoders. I was hoping to spend about $650 on a brand with a good reputation. What I found were only receivers at this price level (and lower) and the AV-550 tuner/preamp at $850, ($1000 list). Believing spending $200 more for equipment that did not have 5 amplifier circuits I had to be getting something much better and actually have more expandability (granted at high cost). I was within moments of buying when I learned that the AV-550 does not have a headphone jack something I only then realized was required. At this point I inquired about Marantz A/V receivers. I learned that SR-680 was the same price. Recognizing that I would not get the amplifier section for free I asked the salesman what are the differences amoung the Marantz A/V line. He did not know all of the differences. He mostly made generalizations and assumptions that I could have made. I tried to be specific but my questions were limited to what knew to ask, such as. Is the preamp the same in all the units? is the tuner? The salesman said he wasn't sure but he believed they were the same in the SR-680 and the two receivers above it but there are probably better electronics are in the AV-550. Then, I asked if there are any diffences in features amoung the three receivers.
The salesman said he did believe this to be the case except for the output of amplifiers. He still did not sound sure so I looked at the Marantz press sheets and did not spot the differences, myself. Since I knew I was not going to buy the AV-550 and did not want to spend more than $850 I bought the SR-680. (I could always return it later, minus a 15% restocking fee. I know a gamble).

When I finally had something at home, (well you know how I feel about the SR-680). I was pleased. Below is most of what I evetually learned that I did not prior to the purchase.

- The SR-680 provides switching for composite video only (not S-Video. The
other receivers do).

- Only one room can be controlled the SR-780 and SR-880 can control two rooms.

- The SR-680 does not have THX processing. It does have Lucas Film type Cinema RE-Eq. (I do not know about the other receivers).

- The SR-680 does not have multiple, room, simulation settings like the other
receivers. (Although, it does have a hall setting and various, time, delay settings are available).

- The SR-680 has only one tape monitor. (I believe the others have two).

- The SR-680 does not have a phono section. (Was not an issue for me and I do
not know about the other units).

- According the press release the SR-680 provides 60 watts of power on all
channels. The owners manual states that 65 watts are available for the front
channels, both driven. 80 watts for the center channel and 70 for the surround channels (presumbly not when all channels are driven simultaneously).

- The AM Tuner is only a token and is the only part of the SR-680 that did not
sound better than my old NAD, (probably not as good in this case but I do not
care about AM).

- Using the Marantz as a receiver, without my external amp, the sound is even
clearer, a little, but with less bass authority. (Upgrading my interconnects
allow me to keep the amp with the extra bass and the clarity is almost the
same but it is still a trade off).

- The SR-680 does not come with Marantz's Remote Control 2000, MK II but rather a more typical programable remote.

- There is a 4th Marantz, Dolby Digital receiver, the SR-580, that I did not know about before my purchase. Curiously, it is priced lower than the SR-680, ($699 I think), but has S-video switching, Multi Room effects and 60 watts per channel.

In closing, I kept the SR-680 mostly because it sounds great but partly because
my dealer requires a 15% restocking fee. Under better circumstances I would like to have had a chance to try the SR-580 which was closer to my target price.
Sonically, I would give the SR-680 about 4.5 stars. Since I only use it as a Stereo Tuner/Preamp I would have to figure in price/performance and call it 4 stars.

This system is a great starter for anyone beginning to gain interest in high quality audio components. For the price and quality, you can't beat it.

I bought the 680 last week for $450.00 (store demo). I replaced a Technics SA-AX920, which the Marantz puts to shame. Before buying the Marantz, I compared it to the Denon 2700, Yamaha 992 and 795, and an HK (don't remember the model number). Granted, the 795 has DTS and S video hook-ups, I liked the sound of the Marantz a lot better. My TV has S-Video hook-ups, so I use those. I mainly use my receiver for home theater, listening to DVD's. I am running PSB Alpha's for the fronts and surrounds, and a 200Ci for the center. The Marantz does an outstanding job!

This is a follow-up to my March Post.
My appreciation of the SR-680 has increased. Everything I originally liked about this receiver I like even more now, 9 months later.

In addition, I now use the Dolby Digital capabilities and love it. The SR-680 works well and is allowing me to build my home theater system slowly. I have only added surround speakers to my left and right fronts. Configuring the receiver for no center channel, or phantom center, I have no problems with dialog, (except at low listening levels). Bass was lacking so I drive my front speakers with an NAD 2400THX 100 watt amplifier. Adding a subwoofer will allow me to return to the receiver's speaker outputs which deliver more detailed sound than the NAD.

Dolby Digital is amazing. The surround effects are very convincing. Transistions from front to back are smooth without "holes". A couple of good demonstrations are on the "Dune" and "Ladyhawk" DVD. In Dune Paul Atreides is tested with a Fighter drone. You can clearly hear the lance thrust from center stage to directly infront of the listening position, ie right at you. In Ladyhake two or three times horses gallop over the viewer, (very aggressive surround effects here). In both DVDs there are not just direction cues but also depth cues.

Not bad for only 4 channels instead of the full 5.1.

In my opinion the SR-680 rates a solid 4.5+ which rounds up to 5 as opposed to my earlier 4 stars

I have just bought the Marantz SR680 two days ago. This was to replace my Sony STR-DE415 AV Receiver. I can say that I've come a long way since I started my system which consist of a one-box home theater solution and was quite impressive initially. But before I delve deeper, my current system consists of a full range Tannoy speakers (M2 for fronts, MC for center and M1 for rears), Kenwood SW501 Active Sub. I must say that I have a very consistent and impressive set of speakers considering the price level. And of course with the addition of my new Marantz SR680. I bought the Marantz for RM1800 (US470) which was a real bargain. While searching for MY right receiver, I came to almost every model existed; Yamaha RXV-495a, RXV595a, RXV-795, Onkyo 575, 656 not to mention Denon AVR1120, 1420. Right from budget range to mid-price level.
The Yams were too aggresive and bright when pushed hard (11 o'clock) and imaging were not too good. The Onkyos have better imaging especially 575 with impressive attacks and good channel separation BUT was a bit too forward and bright for my taste. The Denon is everything between the Yams and Onkyo with clean rear channels. I don't give much emphasis on wattage as this does not relate directly to sound quality.
Actually I was not really into Marantz AV Receiver until I auditioned the SR680 which totally caught me wrong footed, in other words taught me a lesson in Home Theater experience. Firstly, the imaging was simply stunning to say the least. The harsh, glaring treble was gone replaced with a fine sounding smooth but detailed treble. The mids were amazing. One thing I noticed was the Marantz were especially good in vocal reproduction. Clean and without a hint of chestiness. But one thing which was lacking a bit; the bass department but solved if u have a subwoofer
I use mainly in Pro-Logic mode which I must say very impressive with good channel separation with smooth mids and treble. This doesn't mean its undynamic. Its attack when called for, is impressive. The SR680 simply let the soundtracks and sound effects flow out from the speakers. Even when I crank up the volume, the Marantz is still as graceful and never once let down its guard.
The remote is programmable and quite good but not super unlike the MKII. Very usable nevertheless. One quible is a lack of an extra MENU button (for programming) as this is now common to all equipments. In other words I have to use another key like MEMO to take its place. The set also lack S-video switching. Only composite type. It has Pre-Outs for all 6 channels so that it can be paired with external Amps. It's not DTS ready. It doesn't have a multiroom facility. However all this was minor quibble to me as SOUND QUALITY is my priority. A Receiver with all the above features and mid level sound won't do any good.
All in all the Marantz SR680 is a highly impressive receiver with very good music and movie soundtrack reproduction. I believe the Marantz ad. now that we don't have to be a millionaire to experience high-end quality. I will purchase a DVD soon and experience Dolby Digital knowing that it will give me the sound that I need (I heard its DD performance during test listening) and searched for all this while. I rate it 5 stars, case dismissed...