I'm running a 5.2 with the fronts and rears being Definititive Tech. Its not their crazy high end stuff but, it is the step or two above the Best Buy crap. I had Klipsch however, unless you listen to alot of rock music really loud you lose far too much of the crisp highs. The down fall to some of the Definitive stuff is they lack bass, unless you get the nice ones with the subs built in. That being said I have a Rokit 10" 250w sub and I built up a 500w Infinity which should(
www.hometheatershack.com/forums/) hit around 20hz. The reciever is a 6.1 Yamaha htr from a few years ago. So far, I love how things sound. Everyone I know loves to come to my house and watch/listen/feel movies, everything sounds great.
What I learned... dont mix different speakers, Klipsch sound good loud but they are rated somthing like 3db louder than Infinity or Def Tech so, they drown everything out.
If you can listen to everything for a while before you but it, DO IT!!! Bring in your own cd or ipod and listen.
Do some searching on the link above, they have some great reviews on there. Best of luck.