BTW, ATC and Bel Canto make a marvelous combination.
I haven't tried so I really can't say either way - although Bel Canto has the power needed and it is a respected brand. I think the dealer above is mostly concerned about Class D amp design and lets face it - nearly everyone has an opinion or bias on amp design (from tubed single ended to Class D everyone seems to have their preferences). I suspect however Powerstudio's problem is more with the speaker as I would not be surprisedto hear that he has already checked it with another amp - at low levels in a near field position you are only going to need 40 watts.
In my experience source problems with ATC tend to show up more at loud levels - digital hash, a poor recording, amplifier distortion all become annoying due to the forward midrange (like with a horn you hear it - nothing is sugar coated).
Another caveat is that, as a general rule, louder (as long as it remains without distortion) always sounds much better. This makes it hard to listen without inching up the volume. Inevitably, ATC users nearly always end up listening at louder SPL's than those with other speakers. Some people say it is the way they are voiced (light bass) whilst others argue it is because they don't distort as much as most speakers. Perhaps it is a combination of both.
Along these lines, however, it would be nice to know what source Powerstudio is using or has tried?