I installed the AAI-NIS PAC box thingy in my 05. Plugs into the head unit were the satelite receiver would. (FYI it's either factory sat or this thing, not both) Has far cleaner sound than an FM modulator.

I like mine, has 2 inputs so you can run both an I-pod etc and an aftermarket sat reciever through it. Easy instal, took about 15 minutes. There is a great post with photos on how to get the dash off on this site if you search.

Found mine on an Ebay online store for 74.99.

I'm cheap so I went this route! I agree with CDDiG that it might be wise to go aftermarket instead of the Nissan factory unit if you have a bit more money to spend. Good luck!