Concerning amplifier differences, I originally bought a very cheap Sony 100wpc receiver from Newegg for about $150. Then I sent this back, and purchased a Pioneer Elite 110wpc from BestBuy for $640. The difference was amazing. I only had a single pair of M22's at the time, and I got a much fuller sound with the Pioneer. With the Sony, I got good mids and highs, but was severely lacking in bass and power.
I think that a good power supply probably goes a long way in sound quality, because that's one of the things that was light with the Sony.
