The DM RMC-100 room controllers have IR and RS232 control built right into them and I would recommend using the RS232 to control the displays. The bell boxes have to be controlled via IR (there is no other way). The good thing about these is that they never actually shut off they just go into a power save mode. To get them back into sync you just have to press Enter on your MLX-3 to turn on the box.

The DVD player will be controlled either RS232 or IP depending on the installer and Apple TV will be controlled via IR as there is no Power.

Looking on the Crestron website there are 5 listed elite partners but there will be many other dealers in the the area. Contact crestron and they will provide you with a list of dealers in the area as I don't think there are many (if any) on here.