Thumbs-up for the Squeezebox.
I have a Squeezebox 2 and 3 Booms. Love them, and with the open-sourced server anyone can jump in and make a device. It'd be nice to be able to buy an off-the-shelf device that would work with it...
I know you can slap together a Pi with SqueezeLite, and there are half-decent DACs and amps you can hook into it, but a nice, neat turnkey box (like a Sonos) would be great.