Okay, I think you may be correct with the EX/RF stuff. I know you can use both technologies in a system. the current tstat is RF and can be used with some EX stuff. I'll find out soon as I have 6 RF dimmers and 1 EX dimmer to try and use in my own home.

I don't see why you couldn't use both in a system. I remember they were claiming 100 RF devices, but that was a mix of 70 EX and 30 RF or something close to that.