For a Sonos/Rti system we do following and works well.

Use a Sonos connect. Hook it to a Sonance 875 amp. This is rs232 with a 2way driver. Now add in an xp6 and use rkm1+ keypads with the Sonos basic driver and the Sonance 875 driver.

Now the one connect plays in 4 rooms with individual volume control per room with play pause track forward and track back buttons functional for Sonos control!

Then you can upsell to touchscreens and add remotes if you are doing automation or TVs