ill reccomend something that will save you a lot of time and stress now and in the future.
if your planning on building a six cage unit, you should REALLY consider building each cage seperate.
Say for example your building 6 3x2x1's....build them seperately and strong, slap a heat pad / heat tape under each cage, put all of the plugs into a power bar and use a 500W thermostat to control everything to your set temperature.
This way you avoid wiring for lamps, having one cage degrade quicker then others, etc...
i speak from experience... been there done the massive unit before. its a b!tch to move....
this way you have the choice of stacking all 6 high, 3 beside 3, etc... good for quarantining new animals in different rooms, etc..
even if you decide to heat with bulbs...id advise building seperate stackable units...plus individual units are always easier to construct then a large unit in one piece,
just my opinion though...