I have been growing up with butchers and new rich people instantly bying B&O – as soon as the had the chance – and the high flyers had a B&O-LINK system (interhouse). It is a minimum 20.000$ investment – and you need to really be B&O geeky to use it… Now – with music on all devices – PC, Mac, Phones, iPods – it even more relevant with a system for the whole house – and there are 4-5 systems that seems good like

Sonos Digital Music System VERY EXSPENSIVE
Logitech Squize Box DID NOT REALLY WORK WHEN I TRIED

But as (always) Apple seems to be most simple and first – iTunes in mind – but Airport Express and iPhone with Remote Access is simple and not that expensive. WOW – see this simple Apple tutorial Video