Stay away from best buy installations.

It's like expecting an expensive steak dinner from McDonalds, just not gonna happen.

I've seen too mant Mercedes get screwed up from best buy, circuit city, hi-fi buys.

Call Jim LaPlant, he is the benz sftermarket gadget pro.
404-277-9383.
He can walk you through whatever on the phone, just good luck getting him at a point where he can actually talk.