A swithchable ballast setup would definately be a good idea. Cfl's work great for vegging, but Hid's are by far the way to go for growing imo, especially when it comes time to flower. Heat can be an issue though, so save urself the headache and get somethin with a remote ballast, which doesn't need to be in the grow room with all it's heat, and an air-cooled hood with proper ventilation fans. This way, the temps are well controlled, allowing u to keep the hid as close as possible to the plants and getting the most out of the light itself. Check out htgsupply.com, they got all the light u need.