You can't just "throw in" HID lights. They are of course the best way to go, but require much more ventilation.

The answer is cool tube, and a 250 CFM fan pushing air through it. Air from outside your grow area, close to the floor. Pushing to outside your grow area close to the ceiling, but preferably to the outdoors. Cool tubes are great, because if done properly you can let your plants actually touch the glass. As you probably already know, this is good.

Heat problems are very easy to resolve. More, or at least more efficient, ventilation.