For a space that size you might want to read up on using a bunch of those swirly 100 watt light bulbs. I use both, 400 watt hps's and the swirly bulbs. If you use enough of the bulbs your plants will grow well and you won't have as much trouble dealing with heat from the hps lamps and ballast. Mind you, I'm no expert on these bulbs, but they're reveging some that were harvested a month ago. They like the bulbs... The new babies love them too... I just don't know about flowering, so like I say, read up on them...