I would stick with either NW or OW Cichlid species.
What is your tank size, what are your water parameters out the tap?
If you live in a hard water area with high PH then African cichlids may be the better option due to the fact that you won't need to alter the water chemistry too much to suit the fish.
Alteratively if you have Soft water with low PH then you may be better suited to CA / SA cichlid species. Really depends on how much hassle you want really.
What sort of look would you want with your tank? Planted, rocky etc.. I don't believe most planted aquariums are too suited to African cichlids due to the highter ph level and the digging habits or the fish etc.. I have never kept African cichlids (unless you count Kribs) so I am probably not the best person to qualify this though however.
Apistogramma Cacotoides, and Ramerizi are peacefull dwarf american cichlids which can tolerate medium to higher PH conditions. These would work well with Keyholes also if the tank was big enough for all the territories.
Hope you can make sense of most of my rambling.
Bricko