The suggestions so far w.r.t. surround systems are good, but: Surround systems aren't designed for house parties because the small sat speakers distort fairly easily when pumped up. Even worse, most ppl don't hear it when the speaker is suffering so someone always cranks it up to far at parties.
I know quite a few ppl who picked up a set of old speakers for parties etc. Also makes a solid impression when the speakers are big enough that it takes 2 ppl to carry one.
Put the amp on a plug with surge protection, but not a UPS. Make sure you have a way to mount/place the speakers symmetrically....if you've got a sensitive ear then you will hear it if its not set up symmetrically.
Not so sure about the 6.1 thing....afaik DVD output is 5.1. Probably won't make much of a difference since you can split the center channel, but I'd still go with a good 5.1 over a 6.1