What Dan said. Airport Express will be your cheapest option, allowing you to use your existing Mac/PC. Pair that with an iPod Touch, iPhone, or iPad as your remote w/ the free Remote app and you've got a very solid system. Sonos can do the same but it ain't cheap. Bear in mind that the Airport Express does have optical out.

I've run it wireless and it works great. If you're concerned w/ interference, run it at 5 GHz and separate that band from your normal wifi at 2.4GHz.