I wish I was going to SXSW! I would love to check out the Leon Bridges show. He has a retro soul sound, very old school a la Sam Cooke or Marvin Gay. His song "Coming Home" will be my next iTunes download - just gotta sit down with my "want" list and do some downloading. I haven't heard much else of his, but he is a hometown boy so his single is getting airplay on the local indie station. It is an awesome song if you're into old school soul.
I don't know who else I'd recommend. There are so many new artists and showcases going on there, I just can't keep up. Have fun if you go!! I'm jealous!!