Ultrtherm UTH's from Bean Farm for enclosers 12'' high or under.
If stacking 12'' net cubes, I have the lower one on the UTH (set to 100F) and a 60W
heating element (no light) about 4 inches from the top cube.
You can buy fixture stands that which are height adjustible for pretty cheap at Amazon to
attach your lamp fixture and raise it as high as needed.
The 60W heating element (for reptiles) gives me more heat then a basking light bulb.
But just about all my containers are on Ultratherm heat pads, which are the only ones
on the market I like and are only sold through Bean Farm.
Also, it helps to keep the room temp on your home thermostat in the mid 70's.
I also VERY highly recommend one of these (or one like it):
http://www.amazon.com/gp/product/B004QVP6QC/ref=oh_o02_s00_i00_details
Need to find one that has adjustable emissivity.
This way, you can monitor the temps in any location inside or outside your pet's encloser.