yeah i think it would be very difficult to control temperature in a grow box using a hps or mh especially one of 400 watts or higher. not sure how hot a 400 watt gets but i assume its alot hotter than a 150 watter and my 150 would burn my skin with the slightest touch and keep in mind you are gonna have to keep the lights aroung a foot to a foot and a half above the plants. I personally think the best thing for a growbox is cfls and to do a scrog as cfls cant penetrate worth a crap. But i am not a pro by a looooong shot.