I have a solo cichla with other fish. She seem to be fine with them. I had more fighting when kept with azuls, orino, and another kel. I prefer solo if it's less aggression. I hate seeing fish chasing each other.
I keep my mono alone. It seems to do just fine. I used to keep it with a silver Aro, but they constantly fought so they got sepparated. It's been doing fine ever since. Even though my tank seems really boring now. Lol