I don't really have any idea. I have only ever had girl cats. I think it would be sweet if Harley had a girlfriend!!
But you say John wants on of the white ones so it depends on them. And personality too. I would just make sure to get matching personalities. Or wait. Harley gets into a lot doesn't he. I don't know if I would get to cats like him since you would be clenaing up messes every time you walked in the door!