batta: I am assuming you are talking about the XM commander? As this unit is smaller than the delphi or JVC units, you re privied a few more options. You might think about integrating it in the cigar lighter position. If you post a pic of your interior, I could probably make many more suggestions. And while I agree that Sirius is better, they are both great. If your not a huge NFL fan, I wouldn't worry about it too much.
dooleyuga: You have three options as far as interfaces are concerned.
CD changer--->AuxIn Adaptor
An FM Modulator is offered in both wireless and wired configurations from both providers. This is the poorest in terms of Sound Quality, but is a clean installation. If wired it can be in stalled so that no wires show.
The cassete adaptor is a very simple install and the hole install can be done at home in no time. The most difficult part is running the antenna lead. It will offer the best possible cassette SQ. The downside is the wired cassette adaptor that leaves a jumble of wires laying around. If I remember correctly, the XM Commander comes this way.
I've heard of (somewhere in this forum) but not seen an aftermarket adpator that can be used with the oem CD Changer din connection to convert to an RCA Input. A satelite radio used in conjunction with one of these would be the best way to go. It will provide the best SQ, clean install, and overall my recomendation if located.