Yeah, I would definitely go with a cat three years or older, as that's when their personalities come through, I mean even in the first few years they're still just rambunctious kittens that look like cats.
Our Jake is a 1 1/2 or so according to the shelter, and he is identical to a kitten, he's always ready to play, and if he really wants to play he'll let you know (start nipping feet and such), but he doesn't get into things like kittens tend to, and he doesn't eat things off the floor which is good. From what I know, a lot of cats between the ages 0-2 or 3 still act a lot like kittens, and their adult personalities don't show through until 3 or older.
If you go for an older cat you'll know how they'll act, that way you can pick out a cat who is calmer, and gets along with other cats, to make it easier for your current kitty.
Either way, good luck with your decision!