Finches
I have 3 different kinds of finches at my house---Zebras, Gouldians, and Societies. The Zebras are adorable, but we're working to get rid of all of them because they can be rather pushy--they will pick on the other finches a lot. It's best to keep them just in pairs. (at least thats what I think, since I could never get even two pairs of Zebras to get along..they always seemed to gang up on eachother.) They also breed like rabbits! We have a pair of societies who when introduced pred in less than a minutes...I wasn't expecting that. They are awesome parents and I'm sure they would get along with everyone if they were put with the other finches. The Gouldians are really beautiful, but also REALLY expensive depending on which colors you get....the bad thing about them besides the price, though, is they can be somewhat hard to find depending on where you live, they need iodine in their water (to prevent feather loss), they don't always make great parents, and they are known to have a problem called 'twirling'..right now one of my females has twirling, and chances are she's not going to make it, even though she's been given medicine...it's really sad to watch her.
If I were you I would get societies...they aren't as loud as Zebras but are just as fun to watch, and you don't have to worry so much about them getting along if you decide on getting more than 2...just know that if you have males and females, they WILL breed!