Well, I doubt with all channels driven the receiver still puts out 90 watts power to each. Very few receievers do, especially in this price range. Of course, how big a deal all those watts really are is another can of worms...
My 5200 drives my M50's as mains, and VP100 for a center (no surrounds yet). At one point, before I had a subwoofer, the LFE was being driven though my mains, and I had the rear surround hooked up as well (with the left/right surround being fed through a friends mini-system), and, for example, had Saving Private Ryan playing at ungodly levels (ie, 0dB volume) and I never noticed it sounding stressed. People upstairs and on the far side of the house did notice their windows and floors shaking though.
