Depends on how far you want to go. Original spec STI units are just as poor now as they were then, XT thumbshifters means you can go 8spd to give you more ratios and have a wider range of parts to chose from (just about all Shimano mechs do 7/8/9 spd). You would have to change your wheels but again plenty to chose from out of modern parts. With a quick de-badge, modern rims can suddenly look retro too.