I only have the room and budget for a 6.1 setup but most recievers I see are 7.1. Should I just get a good 6.1 or can I get a 7.1 and run it with a 6.1 set up?
You can run most 7.1 receivers with a single back speaker (or none at all). THX (who introduced EX) believed that a single back speaker tended to collapse the sound field. Two speakers (playing the same tracks) produced more of a diffuse rear soundstage.
I also recall something described here at the HTF that involved people sitting directly in between the center channel and the (single) back surround experiencing some kind of weird effect where sounds actually originating in front of them were perceived to emanate from behind them instead.
So it looks like as long as you have the optimum/100% correct locations (not always available though) to place just two surround channels - i.e. a 5.1 system - and using just the right speaker designs, that would save the trouble of mounting another pair of speakers & of course their additional expense. I've heard a couple properly configured 7.1 systems and they did seem to sound relatively more enveloping than 5.1 but man, all that extra hassle & expense just so a manuevering CG spaceship sounds a little better...........
I actually heard those 7.1 systems at a hi-end dealer here (Denon/B&W) & a friend's buddy's home (Harmon/Infinity Beta system). Mine is a 5.1 system & configured more for surround music playback (different than what Dolby advises for movies, though i think it sounds better for movies than their recommended configuration, though your mileage may vary yada yada ).