I'm just looking for a good shop that won't screw things up and have bolts and **** laying around the car when they are finished.

I have a Bel remote mount radar detector that was installed by a shop in DC in my old Passat. Don't trust that shop to work on the A4 - don't trust myself to install it.

Well I'm either going to get some sort of satellite radio first. Then I'll either want to add a sub in the cubby hole and/or rip out all the Bose speakers and put new stuff in.

Satellite radio installs are easy, if do a sub in the side of te trunk, then you'll need to do a custom fiberglass box, which unless you've done fiberglass before I wouldn't reccommend. Speaker/Amp replacements are also no problem to DIY.

Yep