All I am saying is that no matter how well I ground the Empeg to the car, there is still some current from the disk and the digital circuitry flowing in the audio ground that makes noise in my head unit and that I can correlate to the disk activity, display changes and/or button pushes on the Empeg.

Right. That's a standard, every-day, run-of-the-mill ground loop. It's not the empeg's fault. It's just as isolated as any other aftermarket head unit, and if you tried to add a Sony minidisc player, you'd get the exact same thing. When there's a DC ground loop, there's very little that you can do within the head unit to stop it. It has to be fixed externally by tracing the fault.

Every time you add another component to a car audio system, you increase the chance for ground loops. Start by going through the various steps in those troubleshooting documents. Check your wiring, Lift grounds on various components and connections, etc. Go through everything systematically one at a time.

If you can't mess with the becker system, you may have to add/lift grounds to it or use an isolator. This is all part of the standard procedure for solving this sort of problem.

(You are using a Mark2 empeg, right? Not a Mark 1?)