250W in a closet needs a cool tube. http://forum.grasscity.com/do-yourself/184802-diy-best-cool-tube.html What are your current temps?
Air cooled hood, cool-tube, intake and exhaust fan(s). If your closet is below the attic you could put an exhaust fan in the top of the closet that sucks out the hot air and exhausts it into the attic, but you will also need some kind of intake to replace the air being sucked out. Hope this helps, -L2T