If you want just fish this is my fav. fish to have in one tank: Aulonocara's (Peacock Cichlids) with a nice rocky build up and a sandy bottom.
If you want tangs: both alto comps and calvus would be cool along with, Tropheus Duboisi, Ectodus descampsii (stay small though so maybe not), Neolamprologus brichardi, Xenotilapia, Cyathopharynx foai, Cyprichromis leptosoma, Chalinochromis sp. "ndobhoi", Neolamprologus helianthus, Neolamprologus leleupi, Neolamprologus olivaceous, Variabilochromis moorii. Thats my suggestion
If you want malawis then go with Mbuna.
Just dont mix tangs and malawis! =)