Deep, I'm in the middle of buying the gear to do this myself at the minute. I'll be going for a SB Duet with the main receiver tied to a Denon system in the dining room/living room.
I will then have another SB receiver and some powered speakers in the kitchen/conservatory with all music coming from a NAS.
Problem is finding a NAS that can run the new SB server software. There was a post on AVF earlier from the Duet distributors in the UK but its been deleted now
He was reckoning that Windows Home Server is the way forward over a NAS.