Need help with ventilation help.

I have a grow cab and it is about 3.5-4 feet tall 1.5-2 deep and 2.5-3 wide. It will be growing 2 plants(bagseed) with 12 flouros 26W, mixed color temp. I know this well be enough light, but I really want to add some HID lights and came across low wattage HPSs. I wanted to add 2 50-70 watt HPS lights to be ontop and have the CFLs on the sides of the plants. only for flowering though. I was wondering how many CPU fans I would need to keep this room cool enough to grow during flowering.

Thanks and Peace