Theres a complete system from Yamaha which may fit the bill. (Sorry the name eludes me, but a quick trawl around their website may do the trick) It is a music jukebox (server) and transmits to smaller boxes in each room. Theres wireless adapters that plumb into your wireless network transmitting files from your pc into your hi fi system. Netgear and I believe Linksys do these. Failing that an ipod plumbed straight into your hi-fi can act as a hard drive.