You definitely won't regret the XM Direct product! I did the same thing, recounted here. Did you hide the antenna inside the rear spoiler? This was discussed here, with valuable instructions shown here (he was installing Sirius, but the instructions are obviously the same).

I did have a bit of a bummer yesterday. Waiting in a line at a drive-up pharmacy for a pick-up, and couldn't listen to XM because the big roof over the drive-up blocked the signal! I had to switch to FM radio! Ouch!

__________________