Yeah, I'm wondering that for myself.

Currently running 5.1, but have a speaker cable in the back wall for 6.1 when/if I want to do it. My receiver is 6.1.

I was thinking of another QS8 for the back surround, but maybe a VP100/150 might be better (and cheaper).

Room is 24x36.
Listening couch is centered 14 feet from the short wall, which puts the back surround 22 feet behind the couch.

Hmmm...