I have a 6x6 closet that i converted into my grow room,
I use 3 seperate T8 shop light flourescent fixtures for the young ones, and switch over to a 400W Metal Halide for the rest. i have a HPS bulb as well, but im not convinced it helps at all. other than it runs cooler than the MH
temps are my biggest issue, so think about exhaust... i can never seem to keep a 400 watt from roasting the closet even with exhaust to the attic and intake from the garage. i need a bigger fan/duct setup i guess. 4-5" isnt cutting it