Yes, you can leave your computer in the other room and get kickass sound.

Check out the Slim Devices stuff:

http://www.slimdevices.com/index.html

The Squeezebox costs a couple hundred bucks and has great sound. If you want audiophile sound, the Transporter is the route.

Both can run wirelessly, although I prefer running a length of CAT 5 cable for mine (you can probably go up to 50 feet or more that way).