I have had ground loop problems particular witht he Empeg that I did not get with my Sony. I did have a few issues with my new Clarion, but i worked that out. I recently re-installed my Empeg and found that while I grounded the Clarion along with my 2 amps to the battery I had to ground the Empeg to the stock ground wire to quiet the system down. To make matters worse, the noise gets relatively louder when i turn the headlights on.

Now, the Miata that I drive has the battery in the trunk so i am thinking that the long cable from the hood alternator to the trunk battery causes some funky electrical issues!

But...It is bearable now and takes some work to really hear the whine..

In your case...I would just use the isolators and not tell anybody!!!!! Just let it be and enjoy the Empeg.....