I just installed XM in my car.. I am ordering service tomorrow.. the install was a snap. the only thing is.. if you don't have an XM ready unit, you have to buy the unit ($200+) plus the XM reciever for the trunk (150+ pending rebate) and the antenna ($50). If you don't have an XM ready unti already. Then I would get either the delphi, or the sirrus portable. Keep in mind that they are going to absolutely rape you on install. For my XM circuit city wanted 50 bucks.. and it seriously took me and a friend 20 minutes to install it; nice hourly rate they are getting there. They gave me preview channels before I officially order it tomorrow and the first thing I noticed was the clarity. I was very impressed, and I love the fact I can listen to one channel coast-to-coast.
Good luck
Kev