Base LinuxMCE distribution includes Sqeezebox Control Center aka SlimServer. It allows to build multi-room audio system very easy. But Squeezeboxes are not so cheap as we’d like. So, Dianemo developers (company which offers commercial installations of LinuxMCE and returns back to community a lot of new and fixed functionality) implemented support of several sound cards (including USB ones) on one core or media director. Each card has one Squeezeslave (software implementation of Squeezebox) associated with it. As result using cheap USB sound cards you can build multi-room audio system.
Code to implement SoftAudio feature will be added to the project repository soon. So, hope we’ll have it in some new 0810 update next month.