I'm not sure how space is on your case but if there are no obstructions, you could put holes up top and attach an additional fan inside. I would first get the fan (240mm if possible) and drill a bunch of 1/4" holes so that the fan can pull the air out. If you do this, make sure you take the "measure twice, cut once method." Empty the case. Pencil an outline of the fan (inside the case. Then drill the holes in a standard vent config. Don't forget to drill the holes for the screws.