You have some choices, but not exactly the all-inclusive product you described. You will either need a rack system or cages that can be stacked and heated as a unit.
Because a cage can be used for different species, you have to use the type/amount of heating appropriate for the species. Fortunately for kings and milks, simple undercage heat will work fine. So will overhead heat.
Anyway, here goes:
Check out www.kingsnake.com/visionherp/ for racks. They have a beautiful setup that is really roomy and functional.
Check out www.herpcages.com for stackable, easily-heated cages that are very reasonably priced. He also makes racks, and they are very nice.
Check out www.precisioncaging.com for some more stackable, easily heated cages that are priced reasonably.
There are others as well. Search for Animal Plastics for racks.
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Mark G
Whitewater rosy boas, mixed rosies
Prairie kingsnakes
Cornsnakes
Mtn kings (pyro, agalma)