But yeah.. Say I want a Red Devil / FlowerHorn type cichlid in there for sure.. and the striped raphael catfish... what are some other cichlid tank mates that could live in this size aquarium with the red devil / flowerhorn?
Jacks, Texas, most Amphilophids, Firemouths, Convicts, Jewels, possibly Buttekofferi, RTMs, Jags, Loisellei, Yellowjackets, Pikes, Acaras, Earth-eaters, GTs, Mayans, the list goes on and on ; you could do a lot with that tank with a little imagination and the more caves and hideplaces you build the more fish you can add.
Set the whole thing up with as many caves possible then wait a few days and make more caves after you realize what space you still have left open to make more. Start the bottom layer with long pieces of sterile slate, bridged by pieces of sterile PVC pipe joints and make cave-like arches. When you collect, always figure 2 "stackers" for every long flat bridging piece.
THEN, go out and buy a bunch of juvenile and sub-adult fish and let them fill in the gaps. I generally make sure the least aggressive species are the LARGEST to start off. The nasty ones will grow quickly