Price Paid:  $0.00

Summary:
When I decided I had enough of my old sub I knew that to justify the next purchase I had to A) Get something that was noticeably better than what I currently had. B) Spend a little money to get someething better C) Audition until I was sure that I was making a wise purchase.
So I went everywhere and talked to everyone and audtioned until I was sick of listening to subs. Literally burned myself out on them. I took notes on paper and made sure that I didn't get too high or low on one product until I gave it a fair shake.
So anyhow.... when it was said and done, based on my room size, listening requirements and budget I narrowed my decision down to 3 subs.

SVS SB12+
Velodyne SPL-1200R
Definitive Supercube I

All 3 sounded pretty good live but I narrowed my decison down based on a couple things.....

The SVS is attractive and can be had for about $300 less than the SCI but doesn't reach the bottom octave depths that either the Velo or Definitive did. If I was looking to round some bookshelf speakers, I would consider this sub, but... I have towers and need something that hits lower notes with more authority. it's probably not fair to have included this sub with the other two, but it's been hyped by so many people that I had to try it. It wa o.k. for what it is but it's no match for the Velo or SCI. So this one was out and sent back to SVS.

The Velo was intriguing because of the auto EQ function and remote. It's also slightly more attractive than the SVS and plays much deeper and louder at those deep bass levels. The presets in my opinion are kinda cheesy though. The Velo cabinet is slightly thinner than the Definitive and overall weight is less. Overall performance was very good. Hit pretty hard and could rumble the floor with some deep bass. Just didn't have quite the presense that the Supercube had and in my opinion didn't seem to blend with my Boston Acoustic towers quite as well.

So this left me with the Supercube. Now I know that Definitive gets bashed by I.D. fanboys for giving full range FR specs instead of +/- 3db specs. So I got ahold of Definitive myself and got some things squared away. The driver with (2) passive radiator design is unique and doesn't really eminate bass as much as it radiates bass. With that in mind, it's difficult to lump this sub in with other subwoofers when pacing it through measurement rigours. But even with that in mind, I was given low end FR of 20Hz +/-3 db in an anechoic chamber without side reflection but with floor reflection. If you corner load this sub you can go deeper. High teens on the low side and it'll push it with authority.
Aside from response specs, the amp is equal to the task with 1500W available at peak.
What that means is that it hits HARD.
I haven't heard it distort yet and I drive it at a pretty decent clip. Not full max as that would just be ridiculous but enough so that it feels like it's relocating my furniture.

In my research I found that there's a lot of bias online against Definitive Technology. But you really have to listen for yourself to appreciate how nice there speakers and subs sound.
I'd say the price is reasonable for how it performs in relation to other sub of similar stature and performance expectations. Are there better subs? If better means "plays deeper and louder" Yes, but they're also much bigger and IMHO less attractive. The other side of the question is, what is your intended purpose? Are you filling an auditorium or a living room? I really can't see how you would need more bass that this unit delivers in an average size living room at movie theater or even concert levels.
It's a thumper and a bumper. Awesome unit.

Price Paid:  $999.00 from Ultimate

Summary:
Produces prodigous amounts of extremely low bass. Movie explosions and special effects take on an ethereal quality due to the output and extension from this unit.
Blends well with music to the point that you can not distinguish it's output from your main speakers, but you'll miss it if it isn't there. A proper setup is necessary to achieve optimum results, but that is the case with all home subwoofers. I am very impressed by what this little box can do. There are subs that go deeper and are produce more powerfull SPL's. But only a small handfull at this size and price. The design is rather unique in that it has a 10" driver with (2) 10" passive radiators. Sealed box design.
Chet at Definitive Technology has provided some usefull information on this unit

Main driver weight is 21.6 lbs
Low end response as tested is 20hz -3 db
2" thick front and 1.75" side cabinet walls.

You can't appreciate what 1500 watts of powered bass produces until you integrate this into a home theater and experience it first hand. Simply amazing.

If you have that desire for deep pounding bass and cabinet size is an issue, then this may be the subwoofer for you.

Strengths:
Very low frequency response with high output capability.
Small size lends to easier placement.
Overall weight is around 65 lbs.... sturdy and solid.
Blends well with other speakers.
High and low pass infinitely variable crossovers.
0-180 degree infinitely variable phase control.
High gloss piano finish caps.

Weaknesses:
No auto on bypass.
Heavy weight makes it harder to move around the room during placement.
Should have a sturdy grill for driver protection.
Non removable power cord.

Similar Products Used:
Sunfire True Subwoofer
M&K
Velodyne

Price Paid:  $700.00 from eBay

Summary:
Its so amazing how this subwoofer blends into rest of the system so easily. I did not have to do anything special for placement. I just unpacked it and put it next to my floor standers and the whole system just worked well togather. I tested the response from sub using test frequencies from my amp ranging from 35 Hz to 88 Hz and it took them on perfectly. I don't have anything to test it below 35 Hz so I don't know how it handles frequencies under 35 Hz.

Strengths:
Mpowerful, very tight, blends in perfectly.

Weaknesses:
Grill cloth material is not very durable and you can easily tear it in case of an accident. They should probably have metal grills.

Similar Products Used:
CSW P500, Orb super 8, DefTech Supercube I

Price Paid:  $1100.00 from Home Theatre Company

Summary:
The SuperCube I is the most seamless sub I've ever heard in the price range. You can close your eyes and not know where it is, yet with 1500 watts of Class D you know its there.

Strengths:
Smoooth and seamless. Good crossover options

Weaknesses:
I am constantly adjusting the volume for different formats. That may just be getting used to it and experimenting