S1 to Gallium Geometry question

[yongkun]

Buying a new argon 18 gallium, currently on a 54cm cervelo s1 w/ a 100mm stem.

S1 Geo: http://www.evanscycles.com/product_docu ... ometry.pdf
Gallium Geo: http://nyx.at/bikeboard/_uploads/_ber_e ... _file1.pdf

Based on geometry, should i got for the Small Gallium with a 110mm stem? I am more concerned with the reach; stand over height shount be an issue.

Thanks!