A cat's personality changes so much over the years. It's something that maybe folks who only rescue don't get to see too much. Or, if you take on a rescue cat you may not notice the changes unless you have them for some time.
At 1 year, Jumpy was a total pain. Biting my feet, pouncing on the smaller cats. At 2 he decided I was his 'woman' and took as many chances he could get to hump my leg.
By three, he'd settle down a bit... but took to roaming and would often be away for two days. Now he's nearly 13, he sleeps most of the time, and if I ever want to find him, he'll be on my bed - lazy b***er!
All the other cats I've ever had for a conciderable time, change and mature over the years.
The point is, RattiesRule, if you do get another cat, in 6-12 months their personalities and dynamics change anyway. The thing you should to wishing for and working toward is that they can at least tolerate each other, and if you've got that already, you're laughing.