Since the antenna is used to receive satellite GPS signals for your Navi..the signal is also the same as that of the Xradio signals. As for the X radio...You may in for a major customization of the X RADIO head unit in the MDX dash...Am sure that audio/video professional can do it...and to make it look clean you have to pay a price for it. I just know that the antenna can be used for X RAdio signals.
I need more info here. I have XM and a seperate Ant mounted on the roof. Where did you get the information that the Ant will work for XM? I woudl liek to try that if I can verify that it will work.
I am pulling my headliner to add sound deadining material next weekend ad woudl love to tap into it while I hav ethe headliner out.
BTW XM is great. The sound is not as good as a CD due to the compression but real close. More like a high bit rate MP3 or directv music channels (lacks a bit of bass).