There was a time that the music channels had cd quality or close to it. But now almost all of the Siruis channels are of poor audio quality. I notice the biggest difference when I switch to FM. The FM is so full and natural sounding. Sat radio had a poor Internet sound. The only reason I get it is because it is a free trial with a new car. I never will pay for it because I paid for upgraded speakers in the car and putting crap audio on good speakers does not make the audio sound better!!!
There was NEVER a time the channels were close to CD quality. I've been on board with Sirius since 2004, and the audio at first on many music channels was splashy, rumbly -- all over the place. Over time it got a lot better (still not CD quality) then it got a little worse -- where it is now. I listen at work online with earbuds and at home in the bedroom with a custom boombox for the old Audiovox PNP3 and it's good enough. The online stream isn't bad, and streaming in the car sounds better than the car dock for the PNP3.
Don't get me wrong; I like good sound. For most purposes, this is not great but it's good enough for casual listening. I have my home stereo and music library for the real hi fi fun. :-)