I started my HT3s with two Channel Island D200s (200 watts per channel). Went to a McCormack DNA 500 at 500 watts per channel (nice improvement -- especially in the bass control, but I think it was more than just the watts, it was also a move from class D to class A/B, so too many variables). Finally settled on two Modwright KWA-150s running bridged (monoblock) with something like 450 watts per channel. Improvement over the DNA 500, especially when running the high bias.
I love the Modwright amps, as I said, a nice improvement over the DNA 500. However, for what you can buy a DNA 500 used ($3300 - $3500 on Audiogon) lately, it has to be one of the hi-powered bargains out there.
David