I wouldn't put M22's in the rear unless I listened to SACD or DVD-Audio. From what I've read, the M22's are good speakers and I think it'd be a waste to put them as surrounds in a typical 5.1 DD/DTS set-up. The surround tracks on most movies just aren't THAT dynamic. I think you'd be better off putting M3's or maybe even M2's in the rear.

Big L