The performance requirements for playing music via a squeezebox is surprisingly low, you don't need a fancy PC at all. This means a cheap low cost system will do or perhaps somebody's cast off...
It also means you can locate the PC elsewhere in the house and not clutter up your living space, connection can be via cable or wireless. Control can be local to the SB if you go for the classic or there's the Duet option with the controller or if you have another Internet enable device you can access it via the IP address, I can do this via my smart-phone, a Nintendo DS or the Wii !
A mac mini may be a good idea if you don't like the SB approach but that may push the budget too far?
Listening in a Foo free Zone...
Only a Sith deals in absolutes.