As I've said before, the M22s are head and shoulders over the Monitor line. The particular models I've compared are Monitor 7s to Monitor 9s (in one sitting) to their old Monitor 11s (I think those were their power towers). In the same environment (pmbuko's house) but separated by time, I listened to the M22s. The Monitor 9s were way, way better than the 7s and the 11s, and the 7s were way, way better than the 11s. The M22s blew the 9s out of the water. Much clearer, better sound stage. Quantum leap, really. The only speakers I've heard that sounded as good (or better) to me were Hales (about the same, maybe a little worse, but it's been a really long time) and Magnepans (way better, but way more expensive).
From what I've read on the boards, you would probably prefer M2s or QS8s for surrounds (when combined with the M60s), as opposed to M3s, which are said to have a more laid back sound and are often used for stand alone stereo setups.
You wouldn't have a problem with 6 ohms; I've got an H/K 525 that I'm running with 6 ohm speakers.
