some SA cichlids combine well with others but still others do not... Tough question to answer... smaller sa cichlids like apistogramma and mikrogeophagus are great community fish while others likeseverums and pike cichlids are not...
honestly the best substrate I have used with SA cichlids is a product called Baylee's Better Bottom... it is perfect size for geophagus to chew and a good color to set of some of the striking but in ways subtle colors of many SA...
For more info on SA cichlids look here:
http://www.cichlid-forum.com/profiles/ choose group " South America" then look at the subgroups available.. when you choose a subgroup an new window will open that lists most of the species in that group that may be available... it will take you a long while( as much as a week) to go through it all but may really help with decisions..
Ken