I placed an order yesterday for a 56 cm Mark V and now I am wondering if I should of got the 59. I know there are countless threads on this but oh well. Here's the specs on my road bike that fits me great and the specs of the 56 and 59 cm IRO. I have no idea which one to get. The bike is going to be used for commuting so I want a comfortable fit but still maneuverable. Thanks for the opinions.

Current Bike - 56cm Trek 1500
Top Tube: 56.2cm
Seat Tube: 56cm
Stand Over: 31.1 in

56cm IRO
Top Tube: 55.5 cm
Seat Tube 52 cm (this is what scares me, is it only measured to the center of the top tube or to the top of the collar?)
Stand Over: 31 in

59cm IRO
Top Tube: 57cm
Seat Tube: 55cm
Stand Over 32 in

If anyone has measured their seat tube from the collar to them middle of the bottom bracket and could let me know that would be great.