I would stay away from Mbunas period. Nasty little Bastards. Problem with them is you pack them in and they will still fight to the death, which means you will only be able to do about half the amount you would with other africans. Also you only have 4 main colors. Blue, red, Orange and yellow (Yes I know there are different shades of those colors, but it is still those 4 colors).
Haps get to big and most will get aggressive the bigger they get.
Go with The peacocks. They are the most peaceful of the African Cichlids, they stay relitively small 5-6" and you can pack them in and lower their aggression even more. the key is to pack enough in their so they can not establish territories. You can also get a much wider variety of color in the tank.
Peacock wise you can put around 15 in a 55 and be fine.
I have a 125 show tank with around 80 peacocks and haps in it.