Excellent match with Klipsch Heritage series speakers.
Excellent detail at milliwatt levels.
Ability to utilize several tube types.

Haven't discovered any!

I've been the proud owner of these beauties since late August. They drive my Klipsch Heresy speakers which I bought new in 1976. I've been using various McIntosh solid state amps for the past several years. Don't get me wrong...the Macs are wonderful...but after having heard the Horn Monos, I won't go back. The Horn Monos came with Tesla EL-34's, which I used for about 250 hours...then one tube failed. Let me say that I thought the EL-34's sounded great...on all kinds of music. But...
A friend of mine who is an excellent Hammond organ player (and repairman) loaned me a quartet of Sovtek 6550's. Immediately upon installing these, I was stunned by the definitive difference in the bass region. These tubes have gonads! The kick drum and bass guitar really came alive. Keep in mind...the Klipsch Heresy doesn't have the bass extension of it's Heritage series cohorts, such as the La Scala...but it fares very well IMO. Besides, if I want the lower regions, then I can enable my Bag End Infra18 sub (it responds down to 8 Hz).
But my serious listening utilizes just the Heresy pair.
These amps are a perfect match for my speakers. They really excel at lower volumes...and allow me to listen at room-filling voulmes as well. I recommend these for any Klipsch Heritage series owner.
I'm using the Monos in conjunction with the Quicksilver Full-Function Preamp, the Quicksilver Moving Coil transformer, a Linn Sondek LP-12 with the Ittok LVII arm and a 1st generation AT OC-9 cartridge. Also...Parasound CD/DAC, Studer cassette, Crown R2R.

Customer Service

Ordered a new set of tubes for my pre from Mike Sanders @ Quicksilver.
Have also spoken with Galen Carol...great folks!

Similar Products Used:

For Home Theater....I use the Horn Monos pushing the Heresy pair as Front L&R.
Processor: McIntosh C39
Center Channel: Anique Sound Labs AV-25 pushing the Klipsch KG2.2V
Rear Channels: Jolida JD-202 pushing a pair of ElectroVoice MS-802's
Sources: Sony DVD & HiFi VCR
Video Monitor: Samsung Tantus 42" LCD