Ubuntu Studio is an awesome build for recording music.
http://ubuntustudio.org It comes with all kinds of great tools. My interface works with it and I have USB Hard Drive I boot my work laptop to and use that when I'm out of town for recording and practicing. I don't use it for gigs I really care about because I don't practice with it enough.
You cannot install Sonar on Linux yet, but there are people struggling with it.
IMHO it's not worth it. You can have plenty of fun doing music on Linux without Sonar.