This swap will be more interesting than most. First the good news, your derailleurs are already compatable with the STI shifters as the Energy has a road gear train. The Bad news is that the brake system is pure MTB, and disc MTB at that. It looks like you will need a road stem, drop bars, the STI levers (2200 or Sora 8 speed double series) and a couple of travel agents for the brakes, one normal for the rear v brake that you added and one straight for the front disc.

The Sora or 2200 8 speed STI's aren't too expensive (around $100), the bars and stem can be bought cheap, and the travel agents will fix the brake system for about $30. The alternative to the latter would be a new Avid road disc for the front and a set of cantelever brakes for the rear.

Add in new bar tape and new cables and you can begin to calculate the overall cost. If you can do your own mechanicing, fine, but if not you will have to pay for that too.

You could save some money with 8 speed bar end shifters and Tektro RL520 road style brake levers for MTB brakes.