Do a search for cash and points in the SPG forum, you might be able to get some nice stays even with just 6000 points. Also 50% off certs and upgrades.

Barring that I'd just wait until you have a need for an award and decide on the airline then. Or sign up for the SPG Amex and get the bonus and do a little spending to get to 20k points and get the airline transfer bonus.