idea for bin/bin extension?

[Inter5tella]

figured i'd look through the typical hamster cages to see if I could find any cool ideas to be applied to a bin, and saw this: Amazon.com: Ware Manufacturing Critter Universe Small Pet Expanded Cage System: Everything Else
How easy would it be to implement a similar, second floor concept, using a, say, 50-90 litre bin as opposed to a full 110?? or to use a full 100-110? in terms of tubing, would I need to use PVC pipe and cut with dremel tool or could I use those superpet tubes (ive heard some bad stories about those, thus my asking about them)
or MAYBE, using a 20 gallon tank as the base, and then putting my already established bin on top? I have a 100 litre bin and while Tino has plenty of room to live, I dont feel like he neccesary has a ton of PLAY ROOM, and i've seen so many crazy cool bins and setups you guys have! If anyone could give me ideas, advice, blueprints, ANYTHING, it would be insanely appreciated.