I agree completely with George's assessment as I also own a Mark IIXG PRO and have found the DKC-850 to be a really excellent solution. However, I used the "add-in" method of installing the 850 allowing me to retain all of the functionality of my PRO piano playing ability and the modern features of the E-3/850 models. I'm not a huge fan of DK Radio so far, yet it's not a big deal to swap one cable, make one setting change in the 850 set-up menu and have DK Radio/TV at will. Best of both worlds.
These are marvelous instruments and I probably use/play mine daily. Enjoy.