Hi Laurice,
I recently installed an XM/Sirius radio in my 2005 Signature. I ran the antennae cable from the radio to the driver side pillar where I tucked it behind the rubber window gasket, up to the overhead cabinets, over to within about 10" of where the TV antennae cable went to the roof, where I then came out of the cabinet. I used the same holes in the cabinets that were already there for the co-ax for the TV antennae, but did have to enlarge one of the holes. Then I just took the cable up to the roof through the TV antennae channel. I removed the TV antennae then pulled the XM/Sirius antennae through, mounted and resealed everything with Dicor self-leveling sealant (fiberglass roof). All of the wire is invisible but for about 10" from the cabinet to the TV antennae channel. Looks very clean. I hope this helps.
Moe McKnight