Let me echo the "skip the 7.1" sentiments above. I went from 5.1 to 7.1 and, frankly, the difference is only in the bragging rights (which is to say there is no REAL audible difference).
The QS8s are remarkable in their ability to spread diffuse sound in the rear of the room. Save your money (but pre-wire the room for 7.1 nonetheless, if you are in the walls-open phase) and stick with the 5.1. You aren't missing out. Promise.
I would place the surrounds to the sides, rather than in the corners, too. The design of the QS8s will spread the sound out to the rear wall, which will spread the sound out.
