My space is a little bigger than yours, but I am running a 250hps in a closet, so we're close....with my fans off and door shut, the temp can hit 100 quick. I have an intake and exhaust and still have to crack the door to keep it at 88. Cracked door is not my idea of discretion, so I am still looking at ways to cool it down. Right now, I am trying to track down a Pyrex Bake a Round to rig up a cool tube. You might consider that as well. I am also considering springing for one of these: Sun Systems - - Sun Shield- Cool Sun 6"

I'm a total newbie, but I thought I'd chime in since it seems we are in similar predicaments. Long story short, it's gonna be hot. Work it out before you get your plants, or it gets to be a real pain in the a$$. Good luck to ya.