Technically I do have a sub, from the HT in a box. I suppose I don't really feel the need to upgrade that one first because I'm not used to a *good* sub. And yeah, I wasn't planing on going with Klipsh for that, one of the first thing I learned is "Don't buy subs from a speaker company, buy subs from a sub comapany"
But the center channel is really obvious when listening to the crappy one I have, I actually find myself turning it off sometimes and just going with 4.1 since I'ts really just me most of the time