Well I can't get to the Becker, so running a ground between the two chassis will have to wait for now. I was able to determine that the ground loop ONLY happens when the Empeg is connected to the AUX in of the Becker unit. Even when set to AUX input, there is no noise if the Empeg isn't connected. There are two kinds of noise present:

1. Empeg electrical click-pop-whirr noise that is linked to drive activity, and
2. Alternator whine

Both seem to be related to a ground loop. I disconnected the ground on the Empeg and grounded it to the chassis directly and still had the same problems, so I suspect I will need to have my stereo shop disconnect the Becker factory ground and ground it to the chassis directly, then install a bridge wire between the two chessis, as you have done.

I installed a PAC SNI-1 ground-loop isolator between the Empeg output and the Becker input and it reduced the click-pop-whirr noises to inaudiability, without any noticable effect on the low- or high-end frequency response. I recommend it. It did not, however, have any affect on the alternator whine.

Anyone have any suggestions on what to try next??