Ken,
I have QS8s located about 13 feet behind me as rears. See Mojo's Dojo on Axiom's wall of fame. I have conducted extensive "testing" with and without the rears on for PLIIx music and Dolby 5.1 movies and find that I wouldn't miss the rear QS8s if they weren't there. Direct radiators in my opinion are the way to go for rears placed that far back.
Jakewash and I listened to M80s and Paradigm Monitor 11s. Sonically, there wasn't much difference between the two. As for how M3s/Algonquins or M22s may blend with your Paradigms, I can't say.
