Hi there! Yeah its possible to mix a few Africans with those fish in suitable large tanks. What size tank are your 6 in at the moment? The most commonly mixed African cichlid are the Kribs but there are a few others that could work like the African butterfly cichlid or maybe jewel cichlids but these can be very very nasty. If you meant things like yellow labs or the electric blues etc they do much better in tanks with their own kind or similar. In a few "controversial" tanks mixing has worked but in the total times they have been mixed I would say 2/10 have been successful in the long run.
Wills