So, even if I plug both the Shunyata D6000 and the DPC-6 into the same 20amp circuit, via the two receptacles connected to that circuit, I'll still get the ground loop I've experienced?
I don't think that will be a problem, or if it is, it will be very subtle; but regardless, my suggestion is to start simple with one distributor on one circuit, plug in amps and preamp, test, then farm out. You have to first prove that you have no loop with proper star grounding. I think the problems will appear the moment you introduce the second line, and when you start moving components on it. Proper grounding has to be taken seriously.