For what you've described, I say skip the computer (too broad a device for such a specific application).
You need ReadyNAS + Squeezebox.
http://wiki.slimdevices.com/index.php/SqueezeCenter_on_ReadyNAS
You need ReadyNAS + Squeezebox.
http://wiki.slimdevices.com/index.php/SqueezeCenter_on_ReadyNAS