I recommend building a rack system using the pre finished wood you can get at lowes. It just happens to come in 16"x36"sizes which is exactly the width of a sterilite 1720(i believe) container, and leave ya a 3" lip to put whatever you need in front of the cage. I then use the same finished side boards but in a 30" width, and these are the only boards you need to cut really. Makes a fantastic cage, and you can make the rack hold 4-6-8 tubs, just depends on how long you make the sides. I use one foot of 11" flexwatt for each tub, and I personally go 6 high so i can plug the 6 flexxwatt strips into a 6 way outlet, then that outlet into the herpstat.
I stain the wood to preference, then use SPAR POLYURETHANE to seal the wood. keeps the moisture out and the cage will last decades.
The wood will cost around 100$, and the flexwatt around 60$.