ParamountScapin,

Unless I'm mistaken, the bike you've shown has bar end shifters that are considered by many to be just as good as STIs. I'm not doubting that your bike would benefit from a move to STI but it will be marginally better, not substantially. If I had a few hundred to spend on upgrades for this bike, I'd put it into lighter wheels. That would make the bike substantially better on the road.

Cale