If your growing in an enclosed area like that, your gonna want an aircooled reflector. Get somethin like a cooltube, or or a solar six (which is cheap), or some other type of aircooled hood man. 600w's get hot as hell. I got done doin a grow a couple months ago in a 2x4x5 tent with a 600w cooltube setup. I used a 400cfm inline fan, conected to both my carbon filter and my cooltube (i sucked the air (scrubbed) through the filter, and then blew it through the cooltube, and then out of the tent. Which incidentally, the air was vented into the same room the tent was in. I didnt have any type of heating issues whatsoever once i bought the inline fan. beforehand though temps got to be around 100+ degrees f.
Now im using 2x1000w setups, but im still running both lights with one 400cfm fan. Keeps everything nice n normal, you cant feel the heat at all.
Now, just for reference man, you can get a nice 500cfm inline canlookin fan from HTG supply for around 40 bucks. It works just as well as a vortex, or any other fan that costs 200 bucks for equal cfms. I spent like a half hour talkin to the dude workin at HTG askin questions about the fan before i bought it, and i dont regret it for a second. Its phenominal, and relatively quiet too man.
good luck with your descision, but 600w setup i think would work pretty good for the space you have, but if you wanna go with 2 400's or 1x1000w, you shouldnt have problems doing that either.
-just for the record, in such a small space, growing only 5 plants, i got a little over 1/2 lb dry using a 600w in a cooltube
-good luck man
-K1.