Axiom setup
Methost,
Nice Axiom setup, I am hoping to upgrade to your configuration.
For your current 5.1 setup, you should definately have one pair of QS8s to the sides of the listening position. Check the Dolby speaker placement guide on this site or on the Axiom site.
For the rear surround channels, a pair of M2i's would be a cheaper alternative at $280. They are also more flexible for mounting as they don't have woofers on the bottom.
Several reviews, including audioholics rate the QS8 hightly for both music and HT. If the have a perticularly large room with multiple listening positions, then the QS8s might perfrom better for HT. Also, you would not have to worry about a bunch of holes in the rear wall.