What's a good, affordable sound system for my home?

I just bought my first house, and I’d like to get a great sound system to put in it so that I can listen to music without having to walk around using my Zune (like I did at my parent’s house——they didn’t appreciate The Fray, go figure).

I don’t want to spend thousands of dollars…so what can I get that’s good quality for $200 or less?