When I finally get around to doing mine, it'll be a factory style Mopar kit that'll play right thru the head unit I installed in it which came out of an '03 Intrepid.
www.dodgeparts.com has the kit, and from the looks of it, it'll cost me about $300 to do it.
I'll agree this is the most expensive and most difficult way of getting Sirius, but when it's all installed, there'll be no additional receivers or anything visible, and my thumb controls on the steering wheel will be able to control it.
Out of curiosity, where's the antenna mounted on an '03 D with factory Sirius? A pic would be great. I've seen them on Caravans, and they're about 3' back from the windshield on the center of the roof. Out of all the Durangos I see, not one has ever had factory Sirius.