Ground Loop Isolator- What a Tradeoff!

[thedoctor]

I just had a XM SkyFi installed in my '97 M3 directly connected via Aux In to an Alpine CVA-1005. I had the stereo guys put in a RadioShack 12V Car Power Adapter Outlet behind the OBC in the dash.

Anyway, I'm getting the whine (increasing with RPM) like a lot of people, and read that a ground loop isolator would help. I bought the RadioShack one, and although it does eliminate the whine completely, sound quality suffers a great deal. Music sounds like it's in mono, and I can't even hear talk shows. What a tradeoff!

If I have the RadioShack 12V outlet grounded in the same place as my Alpine HU, the whine should disappear w/o using the GLI, right? Can any of you recommend a good stereo shop in the Bay Area? (From San Carlos down to San Jose). My current shop can't seem to fix it. Or can one of you do it? I'll pay you, of course. Thanks for your help!