I'm looking to buy new pedals and would like to use double straps. I wear soft soled shoes so I was originally considering the GR-9's, but from what I understand the GR-9's don't accept double straps. So now I'm considering MKS's Sylvan track pedals. My issue is that I hear the Sylvans distribute pressure unevenly on the bottom of the foot and can be uncomfortable for long rides. Should I spring for some new shoes (I.E. Sambas) and go with the Sylvans, save up for the RX-1's, or are there any alternative platform pedals which accept double straps?

GR-9's will take double straps, you just need to get longer screws for your clips to help hold the front strap in.

Sambas are great shoes for riding in though. You should get those just for that.