Are you looking to sell your 31"s and still move to 33" I'd unload your 31" if you want. Granted, I may not pay the price (since I loose the road hazard buying used tires...the price isn't always worth it). But I do want 30 or 31s myself. Where the 31s you got the BF G's AT tires?
BTW...the next best I've seen is discounttiredirect.com with the free shipping and skip the stems and all extra stuff. Before that though, call Wal-Mart and ask if they will mount the 33" (off rim, since they are not factory spec). If they can do it...it's only like $10 per tire ($5 mount and $5 balance). That the cheapest and even the super sucky Germantown store here did a good enough job with a few sets I had done for various vehicles.