Note: See following post for more information.
When it comes to chinchilla cages you should be aiming for getting the right size. Some owners go to extremes and build one that's 8' tall. That might be a little bit dangerous for a young chinchilla.
Right now I'm using a Ferret Nation 182 with a divider and have two chinchillas. Mine has been modified but aftermarket metal floor pans can be found for chinchillas.
I wouldn't recommend keeping two chins in the divided space but I think it could be done in a bind. It's actually a very good sized cage, although at first I was concerned it would be too small with the dividers. I had to separate my two after they were pulling each others' fur out. I was using it without the divider for a while and it was very good even then too.
http://www.ferret.com/item/ferret-nation-habitat-model-182-double-unit/650431/Anything of that size, as long as it's metal construction, having a solid metal floor pan, or having a wire floor of no greater than 1/2"x1/2" wire space, with wall wire spacing no greater than 1" x 1/2" for adults, and 1/2"x 1/2" for pre-weaned kits is a good cage. You should build wooden shelves for your cage. We do have a section on cages here with some good examples as well.
http://www.chinchillaclub.com/forum/index.php/topic,117.0.html