I didn't try a second pair of QS8s for the back channels (in 7.1), but I did hook up a couple of old bookshelf speakers to try some of that. My room doesn't really have a lot of space for the extra two speakers, but I didn't feel I was losing much sound at all sticking with 5.1 with two QS8s. (also saved me having to figure out how to run and hide the extra cables)
It's easy to over think receiver purchases. Have a look at Onkyo or Denon, and find a midpoint between your budget and the bells and whistles you can do without. (normally stuff like wi-fi music streaming) If you feel like you're going to be obsessive and need new processors every few years or so, you might want to go the separate amp route.
Outlaw has a new processor coming out pretty soon, which looks like a good deal:
http://www.outlawaudio.com/products/997.html
