I don't know if you have already decided against the sonos system or not but my parents recently purchased it and a NAS (networked attached storage) to store the music on and LOVE it. The setup was a piece of cake (connect devices, put the included cd into a computer and follow the very simple directions). The system connects to streaming radio stations without any problems and plays all the music back from the NAS again without any problems. They have one of the "players" wired into the network and it had a very handy 2 port ethernet switch so they used it to connect the NAS. The other player is powering speakers in my dad's office and is controlled wirelessly.
It sounds good to me, but take that with a grain of salt since I really have no audio experience.
The UI on the controller could be a bit more responsive but its not enough to annoy them (or me), just enough that you still realize it. Also, the Sonos system is expensive (1G for 1 "controller" and 2 "players"). You could save money by not buying the controller and only getting one player as the software to control the system seems polished and easy to use (I actually prefer it to the controller). Another annoyance is that every once and a while something happens to the permissions of the music files (could be any number of things mucking it up including me
) and the Sonos "controller" complains it can't read a music file. A quick music update solves the problem but it's annoying to have to rescan the music library and the rescan may become an issue as they rip more and more cd's to the NAS.
One thing of note: the NAS didn't come with the Sonos system and was purchased separately. If you do buy a NAS consider buying one that has two drives instead of one so that you can use RAID in mirroring mode. That way if one drive fails (which seems to be happening more and more as drive capacities go up and tolerances go down) you don't lose all your data.
Sorry if this sounds like an ad, for a while we had a computer that controlled the in home stereo; it was nice and did what we wanted, but it wasn't near as easy to use and was constantly having issues (I hate updates now). Plus, the Sonos system is a new toy so I'm sure we'll find more things we don't like about it as time passes.