As others have said, don't worry too much about frame size. Theoretically, I should feel most comfortable with a 56 c-t, but I've got bikes ranging from 55 to 60cm c-t with different stemsizes and seatpost-length, obviously, and they all feel comfortable even if my riding position is quite different from one to the other. Much depends on the use; some feel better for hilly rides, others on cobbles, etc. All this in function of relatively short and 'leisurely' rides. Of course, if you're talking 6 hour rides at competition-speed, things might get a little more critical!

Joseph