That sounds like a nice tank! It really depends on which species you pick as to how many you can have. Since they vary in size, aggression and in diet, it is important to plan what your mix will be. Personally I prefer to buy my fish in groups, many live in groups in the wild. I am not very good at telling you what to pick, but better at telling you why or why not they will get work in your tank. So do you have a list of cichlids that you are considering, or already have? Since you can't reply to this message, just start a new message and we can discuss your tank further.