What's the temp in the room with the light on? anything 85+ will stunt the growth hard. How many plants do you have? Id go with a 400 watt M/H during veg and 400 watt HPS during flowering for good light spectrum if you dont have more then a couple plants.
GO in the attic....cut a 4 inch diameter hole in your AC and drill a 4 inch hole in the top of your room and connect it. You gotta have A/C if you are not growing during winter.