Best answer by Chris
1. Watching TV - always then rears act as surrounds
2. When listening to music via Sonos app - the rears act as a full stereo pair.
Ambient Mode - No Switching
1. Watching TV - rears act as surrounds
2. Listening to music via Sonos app - again rears act as surrounds in a dolby prologic type where just a little reaches rear
In my opinion there is no reason to have the system ever in Ambient Mode. It should always be set to full mode and leave it in full mode.