Numbers don't mean a thing. I've ridden a wide range of sizes. I currently ride road frames "labeled" 48, 51 and 52. The top tubes of all are within 1 CM of each other.
You need to know what top tube length you need, combined with the stem and bar length. Headset height will also change from frame to frame. Don't order a frame on-line unless you really know how to measure your current frame and compare to the frames you are considering (BTW, nice frames).
Are you planning to build the bike yourself? Do you own the components or buy from your LBS or? If you have a qualified fitter at an LBS, you could pay for a consultation or they may do it for free if you buy the components from them.
Editing to add:

Originally Posted by
moogal
A competitive fit will recommend a small but a more relaxed riding style will recommend a xs size.
"Competitive" vs "Relaxed"- This is a personal decision based on your preferences, riding style, distance, flexibility, body type, hills to be climbed, etc., etc., etc."
Last edited by SadieKate; 12-30-2005 at 09:03 AM.
Frends know gud humors when dey is hear it. ~ Da Crockydiles of ZZE.