I have XM in my car, and Sirius in our new minivan. I would definately say that in both arena the sound reminds me of AM radio. SUPER compressed, as we all know. In our minivan, I only have bass/treble control, so I am pretty much stuck there. In my car, I upgraded the speakers and head unit (radio), and I have a LOT of control over the sound. Now, I can completely enjoy my XM in my car, where before it wasn't very good. So I put a vote in that a key factor is the ability to adjust the sound quality before even sending the signal to the speakers.
I know that I read something in a home theater mag a month or so ago that there are audio manufacturers that are working on decoding software that will try to compensate for the high compression of the satelite signal. I used to have a setting on my old car stereo that would compensate for MP3 compression over a regular CD (which is still compressed I know). It made a big difference. Sure it was guessing at what to add to the sound, but it was effective.
Just some thoughts. Take 'em or leave 'em.
