If SONOS is your one and only source you are probably best using a multi-zone amplifier with auto sensing capability without having to utilize the control system. The isea would be for the client to pick up the iphone/ipad/etc, start playing a song on the SONOS system and the amplifier automatically kicking in and playing over the house speakers.

The alternative would be to select a source / zone with the RTI app, then have to switch over to the SONOS app for control. The AD-8 works best when the client has multiple sources nad multiple zones where control is acheived through the RTI control system.