All you need now is a inline fan to pull the air out, this will make a HUGE difference, but you would need to pull the air out into another room or out the window,if you dont, and just let the air from the cab get pulled out into the room where your cab is, all the air that is being pulled out from your cabs will eat up all your fresh cO2 in the room. If you get a inline fan to pull the air out of the cab you dont need another one to pull air "into" the cabs, the reason is once the inline fan is pulling air from the cabs, little cracks and holes around your 2 cabs will be also pulling in air through the cracks and holes allowing fresh cO2 to come into your cabs and giving you fresh air flow and bringing down temps "hope im not confusing you" this is the method i use for my grow tent and it works pretty good, try to get a inline fan with more then 200CFM, i know its a bit high but why not have extra insurance