I'm so surprised that all of those cats can stand being withn sight of another cat without a fight erupting and sounds from that old game Alleycat filling the air.
Traditional experience has taught me that when two cats see one another they immediately have to yowl for approximately fifteen minutes prior to scratching the shit out of one another and then darting of in opposite directions, only to be seen doing the same thing the next week.
In my experience, so long as cats don't feel they're competing for resources, they will get along. A quick way to get there with a new cat is to set out enough bowls of food that mealtime doesn't feel like a competition. The room may look like the dog room from "Alleycat" at first, but you can reduce the number of bowls after a couple days.