Judging by the distance your surround speakers are away from the back of your couch and given my own testing with the M22s vs. QS8s as surrounds, i would probably go for the M22s in this situation (a direct radiating speaker).
You could use the receiver options to turn up the dB of the QS8s in the back to increase their effect but really, placing your surrounds 10' away from your listening position is pretty far as home theatres go. I think a direct speaker would forward the surround sound better than the QS8s at that distance. In placing my own QS8s too far behind my couch, a surround sound was created that sounded too distant and full of far off echo (even though the receiver had been adjusted for speaker distance).
The sound of a whizzing bullet sounded more like it was whizzing 50 yards out instead of 50 inches past your head.However, all that being said, the QS8s will still work to create a diffuse surround sound field in the back.
link to surround review M22vsQS8
jbz makes a good recommendation to give the Axiom 30d trial a run for its money.
You only have to lose the return shipping and on the small QS8 shipping box, it doesn't amount to much.