In my "man cave," I use a 42" Sony Bravia as my computer monitor and TV. I also have a PS3 connected to it. I bought the
Logitech Z-5500 surround sound with my PC, but you can connect pretty much any audio source to it. It has both optical and copper digital inputs (no HDMI switching). It costs about $210 from Dell, but I'm sure there are cheaper sites. My bonus room isn't very large at 17' x 15' and this is plenty for that room. I have my PC, cable box, and PS3 connected to the Z-5500 controller unit.
I have a totally different setup in the living room, which is quite a bit larger than the bonus room. That room has much nicer and more expensive equipment and I ran all the cabling through the walls. I probably spent around $6k total for the living room setup. Something like the Logitech would be far less than satisfactory in my living room.
Those two rooms have totally different purposes for me. The Logitech setup in the man cave is perfect for me, as pretty much all I do in that room is play guitar, pay bills on the PC, and of course, play games on the PS3.
VandyZ and jeffie7 gave great advice - DO NOT BUY BOSE. My wife was a big believer in Bose until we moved in together and I hooked all my sh!t up. Now she knows the truth - there are highs and lows and a clarity she didn't know existed on her CD's and DVD's. avsforums.com is the best resource I've found for audio/video, and if you get your cables anywhere but monoprice.com, you're wasting money.
-djb