I have to agree with all of the previous responses...$300 is a pretty tight budget and a decent sub wilI cost that much and more.

I haven't heard them myself but the HSU Ventriloquist 6.1 system(which comes in various 5.1 and 6.1 configurations) got a very strong review in the last issue of Home Theater magazine. There appears to be some real thought and ingenuity built into the system and it's pretty darn inexpensive as well.I think the system in HT was going for around $600 (directly from HSU) but you can get it down a little cheaper by going with their smaller sub and dropping one of the rear surrounds.

Or you could go the slow and steady route and get a nice sets of mains and a timbre-matched center channel in the beginning and add to it slowly. You most-definitely need a subwoofer to receive the real bottom-end in DVD's so don't hold off too long.