I have a male salvini in a 55, and he has allowed a male firemouth to live in there with him. They have tons of caves/cover though. The only other fish he will allow in there are some giant danios and a few corys. The salvini has control of a cave that runs about half the length of the tank and he usually does not allow any other fish inside. If they venture in he makes sure they don't stay long.
I ve had sals with sevs,oscars,convicts,jewels,jd,turtles,firemouths and singley are fine with anyone but as a pair will KILL any thing.. but as parents they are amazing!
I had one with a jack Dempsey when I first got into cichlids and it worked but the jd was the boss and very passive if tank mates minded their business this was in a 55