Hey Fly.. the ballast is the part makes the bulb actually work and does not cool it. Check out the section on electronic ballasts on wikipedia..
Electrical ballast - Wikipedia, the free encyclopedia
I think a lot of people like to cool tube style reflectors and a remote ballast. The cooltube lets you draw air through the tube.. usually about a 6" one.. and over the bulb.. then out of the grow area. That way.. you have no heat issues.
If you look on hidhut.com they have some under the lighting kits i believe..