Swap the tires to skinny road tires. That's all you'll need. Well, and tubes that fit the skinny tires. Seriously, the tires alone will make like 95% of the difference. If you want to be able to go offroad easily, a second set of wheels will help so you don't have to constantly mount/dismount tires.

The stock components are more than adequate (the new Tiagra components are actually quite good).