I'd definitely go to dual subs before worrying about 5 vs 7 channel (altho I didn't do it that way). In my living room when setting up a 7ch setup I experimented briefly with both front heights and rear surrounds where I could switch back and forth and preferred the rear surrounds. Some day I'd like to try front wides, just haven't bothered, as from what I've read that seems to be a better way to go in general. Never tried buttkickers.
"I realize that somebody playing free music isn't as commercial as a hamburger stand. But is it because you can eat a hamburger and hold it in your hand and you can't do that with music? Is it too free to control?" - Don Van Vliet (aka Captain Beefheart) discussing commercial success in the music biz