Ah--now you're discovering the joys of this hobby. I'm relatively new at this myself, but I think I might be able to confuse, I mean *help*, you a bit more.

One of the beautiful things about audio/video is that you can always upgrade as your listening preferences and budget allow. Since you already have a center and surrounds, I would go with a pair of bookshelves and an inexpensive subwoofer. If you do listen to a 65/35 mix in favor of HT, you will definitely want a sub in your setup--it changes everything!

I know a lot of people on these boards swear by Hsu or SVS, so I recognize that I risk being stoned to death by saying the following. My sub is the Dayton Audio Titanic from Parts Express designed by Vance Dickason. It comes in kit form, so you have to do some basic assembly (about 1 hr), but for $350, you get incredible 250-watt bass that sounds like it costs triple the price. I use mine for HT and stereo with my M60s, and my father uses the same one with his Magnepans for stereo--we are both thrilled with the value of this subwoofer. All I know is that it works well enough for my Hispanic neighbors to complain that I play my Santana CDs too loud.

With your remaining $350, I would get a pair of bookshelves from the Axiom outlet (pick your favorite). You should have no problem with bookshelves in your size room if your amp can drive 'em. One caveat here: the Axioms will sound a *lot* more open and detailed than the Infinity center channel, so you may not get great timbre matching. It may also not work out so hot for movie effects that pan across the front of the room (like the jets in Top Gun). Use your judgment here. This is a problem you can correct later with an Axiom center channel if you find it necessary to do so.

The back surrounds are almost a non-issue. I use Infinity Studio Monitors that I've had for a few years, and they work just fine.

I hope this helps. I'm relatively young, so I know what it's like to try to get started on a budget. Regardless of what you do, most anything is going to sound better than the Bose cubes. Just be patient, and most importantly, have fun!