Are display cases strong enough?

I'm looking to get more big cages so that i can expand my monitor collection but I can't build my own right now and don't want to spend 500+ ea on prebuilt cages. I really like the look of the display cases, there are a lot of them being sold around me for fairly cheap, but is the glass strong enough? I'm looking at a few that are 70"x40"x20. Look just like the ones at a smoke shop and I've seen people drop things on them in store without any problems, but if i have to add 2ft of dirt and sand would it need reinforcement so it won't bust? What about constant heat from lamps? If anyone that has done this can chime in and post pictures, it would help. Thanks.

I have a feeling that display cases are made of tempered glass, which is the only kind you'd want to use...I think they'd have to be, because no store-keeper would want to get sued if the case broke and injured a customer. I've seen display cases for sale in the past & considered that option myself, but every case is different...if it meets your needs, I don't see why not? That doesn't mean every one of them will hold the extra weight you're talking about...if there's any doubt, why not add support to the bottom? Also, compare the thickness of the glass to an aquarium of a similar size. Do they have enough ventilation? (so they don't over-heat w/ heat lamps etc)