Right now I have a 600 watt light in my closet, inside a cab with the doors open. I have a Honeywell fan that I bought at walmart for 9.99 blowing directly on the bulb and the fan is about 12" from the bulb. My temps are maybe 70, 75 at the most. The trick is to get a powerful fan that is blowing on the bulb AS SOON AS THE LIGHT COMES ON, you can't wait till after the bulb has heated up.

It does such a good job that I'm confident when I get my new cabinet that is 20" x 70" x 48" that I will be able to have the doors closed with a 600watt light and the addition of a exhaust fan. Check out this fan for exhausting hot air, really good deal, 200cfm and it's only 43 bucks. Go to www.homedepot.com and type in TW108 in the seach box.