I use the M50s with an Onkyo 797, Velodyne 10" CT100 sub, Merak MC6H center, Merak MT66 rear surrounds, and Mission 77ds back surround speakers, driven by a separate Denon PMA 500V 2 channel amplifier.
In stereo mode, the Onkyo drives only the M50s and the Velodyne sub. I haven't tweaked the cabling of this system, but it sounds great in either stereo or 7 channel (6.1?) mode.
I haven't done a sit down (run up and down the stairs) comparison between the upstairs Onkyo/M50 system and the Antique Sound Labs MG S1 15 DT/M3 stereo system downstairs, but interestingly, I think they're comparable in musicality. The M3s are wonderful - quick, acurate, lush especially driven by a nice tube amp. The M50s have the same qualities but sound, well, bigger. The mids are still sweet, the highs tinkle and the bass is certainly bigger, although since each system has a nice sub, they both make terrific, tight bass. For HT, I think the M50s are superb. It would be hard to imagine speakers that sound much better than the M50s - although they might be improved by some ultra quality satelite tweeters stuck on top.
I know they sound better than the Infinity Composition Overture 3 speakers with 500 watt amplified subs I used to have. Heck, the M3s sound better than the Infinities did.
