I wish I could comment more on the topic but I don't have experience with other cages than my highly customized parrot cage. The FN double level cage seems to be popular here but you should also order an aftermarket cage pan made for chinchillas. The plastic pan isn't as deep and can be chewed through according to what I've heard though not all chins will chew it. It can hold two safely. If I were to buy a new cage I would try to find something with a wire floor and pan that goes underneath of the floor where the chin can't mess with the bedding.
I wouldn't put more than one chin in the single level version.
Most cages come with ramps and won't come with shelves. You shouldn't use the ramps, especially if they are made of wire. Wire ramps and shelves are known killers of chinchillas and other animals because they can get their feet tangled in the mesh as they fall over the side. Wire floors are controversial but I feel they are the most sanitary and won't cause problems if you have good shelves. Shelves should be made of white pine and can be either ordered online or easily fabricated with a drill, a saw, and some simple hardware from a store. The drill holes don't have to be too precise.
I have read the super pet cages aren't as sturdy as the Ferret Nation but they'll get the job done. Be careful with mounting large accessories such as a wheel to any wire cage as the welds can break if there is too much flexing.
I recommend getting a cage big enough to house a 15" chinchilla wheel if you can.