I believe the SONOS system uses Samba to access music files on a linux box. I don't believe there is any integration with LinuxMCE. One alternative that you might consider is Slim Devices (now Logitech) Squeezebox
www.slimdevices.com. The Slimserver software is integrated into LinuxMCE and LinuxMCE allows you to assign devices to rooms and use the media browser interface to access and play music files. If you want a handheld remote like the Sonos, you can use a Nokia n770 or n800. Both work with Slimserver, but I believe only the 770 currently works as a full LMCE orbiter.