Depending on how many MR points you have, the SPG Nights & Flights might be a good buy. For 60K SPG points, you get 5 nights at a Cat 3, and 50K airline miles.

http://www.starwoodhotels.com/prefer..._checkRoc.html

Of course, if AMEX/SPG does a bonus promo you can transfer at a 2:1 ratio rather than the current 3:1, sweetening the deal even more.