You are absolutely correct!
Sirius called me last week (again) asking me to renew my subscription (they have snail mailed, emailed, and called several times).
I keep telling them that I have No Interest in renewing because of the over compression of their signals. She did not understand what I was saying and said "We are always adding more content" I told her that is exactly the problem. You can only squeeze so many stations into limited bandwidth and that means that you must sacrifice audio quality by compressing it every time you add more channels).
SiriusXM quality rating of music audio falls somewhere between AM and FM to me. Not Acceptable to my ears.
(If you have experience with MP3's you can easily tell the difference between 128bps and 320bps audio files or better yet MP3 and Flac* <-*not playable on these head units).
You can play overly compressed signals on a $20K system (Audio or Video) and it is not going to make it sound great.
Throwing money into a more powerful system for your home or car will not fix SiriusXM's issues...Like they used to say "You can polish a turd all you want, but in the end it is still a turd."
The answer: SiriusXM needs to spend money on an upgraded SAT Transponder with more bandwidth such as Dish & Direct TV did to carry the new HDTV signals.
It is a shame that SAT companies such as SiriusXM overly compress their audio signals and think that everyone will accept it as a good option for music. All that profit that they rake in, they should spend some to improve quality for their customers. Until they do that SiriusXM isn't a good option if you are wanting to listen to music. Now if Talk Radio is your style then you probably will not mind the severe signal compression.
The shame is that I really want to like SiriusXM, but as far as their music quality is concerned, I can not bring myself to enjoy it at any price.