400w HPS are very hot, you can always buy a 250w HPS. Its really all about space. Even with a 400w HPS if you don't have enough space you'll be hitting only a small percentage of the plants. If you had a 400w HPS coupled with 9 floros the heat would be insane unless you get some really efficient ventilation. Heat becomes a very big problem with HPS. What i'm saying is the strongest light will be the HPS. So you could get a 400w with a few floros or 250 with more floros around the sides. Up to you really.