The look a little the same, with the vert. bars, only prob I see. My male white top afra and hongi didn't appreciate each other in my 150, so the afra got given away as I didn't have females for him yet. I'll maybe one day trade the hongis off for cobues, I really like them too.
Although I love each of those species, there is no way that those guys will get along in a 55gal. choose one of those three (the one you like the most) and then pick two new species.....just my 2 cents