My previous 7.2 system used 2x M2s in the back surround position (FMB aimed down a few degrees) 2xQS8s in the side surround positions, and a pair of M60 like Michaura M665s up front (2 subs, SVS 20-39 and a Velodyne CHT10), heavily modded Merak center (2x6.5" axiom drivers and a horn). It all sounded pretty good, but the M2s in the back position were a step down in sound quality (HT) from the pair of Mission 77ds speakers I used before - it could be the M2s didn't like the high position as much as the Missions, dunno.

Enjoy the Music. Trust your ears. Laugh at Folks Who Claim to Know it All.