If i had to give the sound an equivilent mp3 bitrate i would say it's between 128 and 96 thats for the music only, comedy and talk channels are probably 2/3rds that.
About 12-13 years ago I had my sportster 4 sirius tuner run via the headphone jack and rca adapter into the ai-net on a Alpine CDA-7873 the sound was pretty damn good. Mind you I was only using the built in v-drive amp to push some mb quart discus 5x7's.
I'm gonna miss the current satellite radio i have (alpine deck with outboard tuner) when i put in the 6+ side slider kit in my truck, the itunes tagging and shazam helped me discover alot of awesome music on the electronic music channels.
This is all just my experience, not sure how your system will react.