If you get the NX-8E the 584 board is already installed. If you get the NX-8 (I don't think they sell it anymore) you will require the 584 board. You will also have to spec a crestron processor (QM-RMC is the cheapest and was suggested to my from Crestron). I do know some ppl on here have incorporated the whole project onto the same processor with no problems but I would be hessitent as I have seen some wired things happen with the security system and a processor.

Don't forget your programming time. The good thing is that the Crestron Module is already built for you so you only have to add partitions or zones to the project along with an intersystem communication (RSD).