Hey, I have the same setup, but with an XM RoadyXT. The XT is small enough to lay flat in the ashtray space.

I'm assuming you did what I did and ran the line-out to a line-in on your head unit. The buzzing can be cured by using a Ground Loop Isolator (GLI) put in-line between the line-out and your head unit (I had it, too).

Here's a link to one at Radio Shack

 

My XM radio made a lot of noise when I put it in my car. I was using the fm transmitter initially and switched to hard wiring the reciever into the head unit aux ports. That stopped all the buzzing noise for me.

 

Mine is hard wired still buzzing, I will try the GLI idea. I diddnt even bother to try the fm modualtor route, I heard to many bad reviews.

 

What brand/price is your steering wheel. I reeaalllyy like it

 

I have to agree with Wolf and 944guy, create a finite baffle for the speakers to improve bass response.

 

Its a MOMO wheel I paid 180ish on ebay plus 45 for the adapter.

 

I just picked up a ground loop isolator this evening. It worked great!

 

Great to hear - enjoy your setup, it really looks awesome!