I recently bought a Garmin iQue GPS unit. Let me start by saying I don't know how I lived without one. It works great and I have yet to get lost with it. Here's the thing, the car cradle made for it is less than perfect. It tends to fly off the dash under hard acceleration or rough roads. It is also neccessary to use the antenna from the unit itself which can have a problem tracking satellites at times. I would like to hard wire it to my truck. I plan on buying the alternate mounting unit from Garmin and taking it apart. Since my truck has XM and no On-Star I want to mount the speaker where the On-Star mic would be in the headliner and put the aux antenna that Garmin offers inside an XM cover to keep the roof symetrical. Do you think it would interfere with the reception?