Well, each one is going to be different. I've heard people say that some cichlids will claim a whole fifty five gallon tank to themselves! You can prevent this a number of ways. The more hiding spots you have the better. Put as many caves, plants (fake ones, as many cichlids are omnivoires) as you can. Don't skimp on this or you will not be able to get as many fish into the tank as you may want.
Also, and this is important. Get all your cichlids at the same time. You don't have to get them all at the same store, just don't release any into the tank until you have all the ones you want. This way, no one fish will be able to claim a territory before another. I made the mistake of getting one red zebra and keeping him for two months before I got a blue zebra and an auratus. The red zebra was not pleased at all. I had to remove the blue zebra, or he would have gotten killed for sure. If I had gotten them all at the same time, I don't think I would have had this problem.
If you are only getting one species, then you will probably be able to get more into your tank than if you picked ten different species. I'm not %100 sure of this one, but it sounds good, no?
Finally, I would reccommend that you make your filter dump the water into a mostly open space section of the tank. My red zebra loves swimming in the current. He also doesn't really grab food that floats on the surface. He waits until the filter's stream grabs the food and pushes it under. Then, it's a moving target for him to hit. He sits at the bottom of the tank, where the stream goes and gobbles the flakes as they flow by him.
