Just installed the factory Siruis unit with the optional aux box today. I tell ya, it was a PITA. The factory NAV headunit weighs a ton. Just getting it out of the dash is a monumental task on its own. Any how, i decided to ditch the instructions since I didn't want to dismantle 1/2 of the interior per the instructions just to hide the unit in the trunk and run the cables up front. I decided to mount the antena on the dash just in front of the center channel and hid the Sirius module underneath the passenger seat mounting bracket. Works well and reception is about the same as the unit in my Speed 3 with the factory external antena/hump.