My 603 S1 seems to work well off a Yamaha DSP A 3090 also an A1 and an RX-V1 are not too far behind.
I have it running off a denon AVR 1910 now, and it seems a bit lacking midrange. Its fine mind you for music, especially rock and metal and classical. Just no baritones or a lot of dialogue from movies etc it seems to fall flat.
Cool.
Srinath.