Cories are such friendly fish...if you can find some healthy stock, how about adding some hatchetfish for the top?
Cory cats are wonderful in groups...remember when you get your larger tanks that the different species of cory cats tend to like more of their own kind....they don't really school together with other types of cories. Your emerald is the same species as the albino cories most lfs sell though, so you could have green and white. I have kept 21 of these little guys in a 125. They do grow to 2 1/2 inches give or take depending on male or female (females sometimes closer to 3). The more of them you have the more secure they feel and thus the more active they are. They tend to play follow the leader more so than school though. One will take off, then another couple follow...then finally a string of green and white darting around the tank.