If it's a breeding pair they should really have their own tank. Otherwise they can be kept with similar sized cichlids whos aggression levels lie within the same range.
I would not recommend a red devil with a convict. Your convict will be destroyed. Red devils are the meanest fish alive. In a very rare case , maybe yours , a red devil can live with others ,usaully a female. Red devils seem like cute little fish as juveniles than at about 6-7 inches all hell breaks loose. Red devils usaully can not get along with other red devils. A red devil will desroy your convict and an oscar. Even if raised toghether as babies as the devil matures it will take the tank as his own .
I recomend a convict with a red devil/midas anyday, my agressive devil lives with 7 of them, they get along fine as long as they dont travel into his "patch"