I have a DC6 MarkIIXG Pro that I upgraded with the DKC-850 and it works perfectly with DK TV and Radio services when installed as a "replacement" unit.
Because the MIIXG head unit has superior sampled instrument voices and the ability to record 6 tracks of accompaniment I often run the 850 as a "add-on" which also give me an additional set of voices from the 850 unit plus the ability to play/record DK Pro files/music. When I want to go back to running the radio/TV features, it's one cable connection and one setting change on the 850 and I'm back online (takes less than 2 minutes). It's sort of the best of both worlds if you don't mind an occasional cable and setting change.