If you're looking to check out something in the new Hard Rock category, check out Sevendust. They just released a "Best Of" disc. One of the beauties of XM Radio is discovering new bands. I've probably found 10 new artists that I never heard of (which you'd never hear on terrestrial radio), not to mention the comedy acts!
My favorites so far are Face to Face and Enemy. Very catchy choruses with very heavy guitars.
Definitely worth checking out!