if you get a inline fan with an air coolable reflector, doesnt have to be cool tube either you can fit a 400 watter in there easy. you would have to duct that hot air out the window/room some how. i ran a setup kinda like in your situation and had no problems with heat. but then again my hot air was vented in the attic and the fan sucked in the ambient air temp of my room into my grow room. got really big buds and great results from it too. also with your space you can easily fit 8 five gallon pots in there. thats if you mount the fan on the wall. what kind of door is it? slider or a regular door? you could cut holes in the door if its traditional, cause those are easy to replace.