If your looking to use sti you have all kinds of costs in your future. First, you have to shell out however much for the brifters themselves, as well as the handlebars and likely a new stem (different clamp size). Once thats done, you have to make sure your derailers are compatible with the sti. If they are, and I can't help you there, I don't know much about sti, then you have brake pull to deal with. The rear you either need to switch to cantilever, or buy a travel agent to change the mechanical advantage of the brake levers. For your front disk, your going to need to switch it out to a road pull disk brake. I know avid makes one. I don't know if there are travel agents for disk brakes.

It'll cost you a lot, Maybe try trekking bars?