CD Quality usually means higher than normal sampling rate, but still compressed to hell to fit through the satellite. It might mean 128kbps or could be even higher if you actually have to pay an upcharged for it. mp3s of 128kbps quality are often called "CD Quality" as is digital terrestrial radio even though it could be 96kbps or even lower. As an accomplished audiophile you will still think it sounds like shit, especially if you play it on your main system Ken. It is fine for Howard Stern though! haha You can hear what these severely compressed streams sound like listening to Squeezenetwork or live365, internet radio stations. Most of them are 96-128kbps.
In the car with road rumble and stock radio you may not notice it when driving. The Sirius programming is the draw, not the audio quality.