Which kind of rodent is a cage like this suitable for?

http://s2.hubimg.com/u/88169_f260.jpg (it's not letting me upload it)

I currently own a syrian hamster in a cage just like that. I was wondering what other rodents could live in it? Because I plan on having more in the future. I've owner 2 syrian hamsters including my current one, a dwarf hamster, and 2 mice.

I'd like to own rodents that enjoy being with other rodents. I would really like a chinese hamster, but they don't get along with others of the same species, and they are hard to get, and they could probably slip through the wires. I did read somewhere though that they get along with other species of dwarf hamsters. I'm pretty sure that cage would be too small for two rats. Would 2 siberian dwarf hamsters be able to live in there? Would they be able to slip through the cage as babies? the mice I had were in a wire cage and they didn't slip through.

Also, if I own two rodents, do I have to get another wheel? And how good is alfalfa bedding? Is there any other cheap bedding better than the woodchip crap?

(I'll post the cages dimensions as soon as I find a tape measurer)