Sonos AirPlay devices are pretty new. Supposedly you only need one, and it can stream to all their devices, but the devices form a cluster, and I'm not sure how

Sonos AirPlay devices are pretty new. Supposedly you only need one, and it can stream to all their devices, but the devices form a cluster, and I'm not sure how intelligent they are about making sure the device that can airplay is the device that's always the master.