Homemade enclosure Heating Venting Q's

I have built a home made enclosure for housing Leopard gecko breeding colonies. 1/2 inch ply with sliding 1/4 inch lexan doors. The whole thing is about 5 feet tall and has three separate compartments one on top of the other. Each comparment is 36x18x20 and is lit with an 18 inch florecent and wired for heat with regular light sockets. My room stays at 70 to 75 depending on the time of year.

I want to use ceramic heat emmiters my question is 40 watts or 60 watts, each cage will help heat the others and be controlled my a thermostat I just dont want to go over board on the heat. Also how many one inch holes to drill for ventalation with out losing the heat.

thanks

KRK