Sounds like you should be in business as long as you can get proper ventilation a.k.a. a fan to blow out the hot air and a way to get fresh air into the room. (Even opening up a window in the room would do!) Just keep your plants at least 12" away from the hps. I would recommend supplementing your HPS with some CFL's. They are relatively cheap. You can go buy one of those work lights, remove the aluminum reflector buy one of those sockets that allow for 2 bulbs in one and watch your girls just love it! Happy growing and Peace!