what else would you intend to use with the 400w cheapest ballast I know for that is http://www.dchydro.com/category/BST0/Grow-Light-Ballasts/okay guys heres the deal hope someone can help. i buoght 2 100w mh lamps and 2 400w hps lamps but i dident know i had to have a ballast. is their anyway i can run these lights without buying the whole ballast setup. thanks