in that case, Either the 400 or the 150 would work, Warning though about the heat put off by the 400. You've got a small closet so I'd go 150 unless you've worked in a real good exhaust system.
I started with one closet too. But once I smoked the first batch, I said "I can't run out of this!!"
I'll tell you now, I cut a 4" hole in my ceiling to cover 2*150W HPS, Hooked up a couple PC fans and that wasn't enough. I'm shopping today for an extractor fan.