I haven't had too much luck with Harman Kardon's for some years now. The last good one I got was an AVR 20 many moons ago. The AVR65 and AVR 310 were disappointing. In any case, if you're going solid state, I'd go with as much clean power as you can get. If you're willing to use your HK as a preamp, how about getting a pair of nOrh/IRD monoblocks at 100 watts each for about $495 for the pair?
When I got my M3s I grabbed a cheap Technics SADX 940 (100 watts x 5, 100 x 2 in stereo) from Frys for just over $100 as a temporary receiver until I got my system. I spent a lot of money and must tell you that cheap Technics just works beautifully with the M3s. You have to pay a lot to get relatively small improvements in sound quality. On the other hand, the Ah! djobie dobie (my new name) CD player does make a big difference.
