I put a Sirius system in my truck a couple weeks ago. Yes it is every thing it is cracked up to be. I haven't listened to AM/FM radio since and rarely CD's. I haven't changed the speakers yet.

Sirius thread

A better site for your questions related to XM and Sirius Club XM

You can do a search in this forum, there are several people that have upgraded to XM, so far I may be the only one with Sirius.