When setting up a mbuna tank the species selection is almost limitless in choices. Start with 4 fish from different genus to reduce the chances of aggression and hybridization between species. Your final stocking number should be around 20 fish after the proper male to female ratio of 1m/4f is followed. Start by purchasing more juvies since sexing young fish is difficult and rehome fish as needed when the extra males are idenified or a hyper aggresive fish is wreaking havoc. Stay away from similar colored fish when choosing like blue barred which will quickly introduce you to how aggressive these fish can be. Here are a couple of links to get started with fish choices. One of my favorite combinations is blue and yellow such as Demasoni and Yellow Labs.
Species Profiles -- Cichlid-Forum
Cookie Cutter - 75-gallons
Synodontis would be a great addition to your mbuna tank as well, my top three would be of fish would be
Synodontis multipunctatus, petricola, or ocellifer.
I've also had great sucess with clown loaches, britslenose plecs, and rainbow sharks with mbuna.