Hi,
I too was a former XM subscriber, and now I am a Sirius subscriber- and I'm staying! They both have similar programs, but like the above poster suggested, you should sample each before committing.
By the way, I also have the Pioneer AVIC-N2, but can't say that I would recommend it, especially if you decide to go with Sirius. I guess if you decide to get XM, it would be a good choice.
The new Eclipse Fujitsu Ten 5495 navi unit with hard drive is definitely something to consider if you want navi/DVD/mp3/Sirius/hard drive.
-Tom