Just to repeat - start small and scale up. We see so many of these pie-in-the-sky setup threads most of which come to nothing, often because the noob grower over reaches and then burns out. Do an initial grow for 4 - 6 plants under one light. Get a feel for it, work out the kinks in your setup, learn the growing process, and then scale up. You will save time, money, and headaches. Plus that way you can get a mom garden going. With that kind of space and lighting you should take a close look at hanging your lights vertically. You likely could reduce your HPS to 600w while achieving significantly better results.