Currently there aren't any pay ahead options for the SoMi chapter that I know of. You can pay at the door with cash or check. However, you can pre-reg all of your character info/magic items with logistics for a 30 goblin stamp reward! Pre-regging also really helps keep a smile on Brigit's (our head of logistics) face! There should be a pre-reg policy listed as a sticky on the boards.
Hope this helps!
~Alison