Be sure to check out the link below (copy and paste it to your browser). There are several helpful articles there on home theater setup. In particular, you'll want to check out the article entitled, Face Off: Surround-Speaker-Configuration Wars. In a nutshell they found that 6.1 home theater sounded best when they used two "back" speakers. As I recall, the consensus was that the best setup used two dipolar back speakers and two monopolar side speakers, but it's been a little while since I've read the article. Good luck with the new system.
http://www.hometheatermag.com/showcategory.cgi?category=Boot%20Camp
http://www.hometheatermag.com/showcategory.cgi?category=Boot%20Camp