I recently picked up a pair of these brand new at a used price on EBay. Very much enjoying them.

I'm using them as part of an active bi-amp setup. They're powering the mid+ribbon drivers of my Magnepan 3.6R speakers. (I have a pair of 1000ASP ICEPower modules on the bass panels.)

These are an upgrade for me, from an Acoustic Reality eAR 502 dual mono block amp, which used the 500ASP ICEPower modules. By contrast, the Bel Cantos use the new(er) 125ASX2 ICEPower modules, which put out about 550 watts/channel at 4 ohms in bridged mode:

ICEpower — Consumer & Professional Audio

It's a definite improvement. I think the mids are about the same, but the highs are much sweeter, mellower, and easier on the ears. With the old amp, there were times when the highs could be glaring or harsh at high volumes. None of that whatsoever with the Bel Cantos.

It seems like the resolution has improved as well, but it's hard to tell without the ability to A/B the two amps.

Anyway, they're highly recommended. I can't speak to the bass-producing features of the amps, but they definitely work well for mids and highs.