I have had XM service for a long time now and love - no experience with Sirius though.
Make the clear channel dominated local stations sound even more appalling than they already do -I never listen to channel 20 which is that kind of drek w/ commercials.
Some of my favourite channels are
4 (the 40's)
8/9 (the 80's 90's) depending on what they are playing
16 - Current country, depending on my current tolerance which is far lower some days
23 (the heart, love songs)
70-73 (the jazz section)
110-113 - Classical
150/151 (The explicit and the family friendly comedy - lots of Bob Newhart, Bill Cosby, etc)
164
(old time radio, I think all they play is radio spirits stock but they still keep a decent selection going)
no concern for the sports sh*t, lex and terry or those things.