I'm also supposed to be at 55cm, 5 10 and 33" seam. I have a 54 and a 56 Allez. The 54 gets you lower with its shorter top tube. I've a 100mm stem on one, and a 90mm on the bigger bike. So it depends what/how you get the bike to fit you. Between the two, I concur with everyone on the 54cm.