If you have the RF system and you want to maintain integration (which I would suggest), you need to buy the Nissan OEM XM receiver. I bought mine from
www.infinitiwholesaleparts.com and bought a Terk XM micro antenna plus splitter.
The install instructions are here:
http://www.courtesyparts.com/satelli...04%20Titan.pdf
Although I used the Terk XM Micro roof mount antenna and went through the third brake light instead of the through the glass antenna discussed in the instructions.
The Nissan XM receiver that I bought uses a two-lead antenna, so I needed to get a splitter with the Terk. The single lead of the Terk was nice for installation, and it has a nice long wire, I think 23 feet.
As you may note from the instructions, the install is a bit of a PITA, although once you get the XM receiver mounted, mounting the antenna is a cake walk.
You already have the NBUS cable under the driver's side dash to connect the XM receiver to the head unit.