I've had very mixed results with the zigbee. If there is no need for frrdback, i'd go 433. If you can give them the OSD from the escient and 2 way from in walls, and talk them out of 2 way volume and sirius on the handhelds, and hav ethem use th in walls for that, i'd go 433.

For me, the zigbee is slow, has remote latency and phantom operation, and the range isn't as good as they say it is, and it takes 3-5 seconds to connect from sleep.

If you know you have alot of RF, i'd do a tester system. Set up 2 remotes with basic volume control, etc, bring them both, and see how it behaves.

That being said, I have had homes where there was so much noise that the RM433 was constantly red.