I know others will disagree with this, but I would get a male. Partly because I like to watch the differences in the two. Even though they will both be fixed, the females are sometimes just so typically female and the males are sometimes just so typically male.

Sometimes it is harder to introduce female to female also, especially when they are older than kitten stage. I know you have a two 1/2 year old now, so if you were to get, say, another 2 year old female, there may be some sparks. However, if you were to get a kitten, she might take over the mother role. But with your description of how Meka was driving you crazy, I don't know if I'd recommend a kitten.

Try about a 4 year old orangie male. They're known to be laid back lovable lugs, but will still be young enough to play when she wants to play.

But also, like Moosmom says, the introductions are soooo important. Do it slow and easy and everyone will be happier all around.