I just use a net book (£150) bought purely for playing i-tunes through my hifi, controlled using “remote” on a free ipod touch.
Although I have now done away with the hifi and use a wifi (not bluetooth) Bose Soundlink, which means I can move the music around the house wirelessly, as it is re-chargeable. I’ve shared itunes with other computers in the household so have access to tons of noise (thanks 22yr old metal loving son!), all still controlled remotely via ipod.
The advantage is that wifey now uses the netbook for her emails etc, so it has more than one use.
All backed up as itunes is copied to each ‘pooter, plus a Buffalo HDD.