Your bigger concern, IMO, is the tank size. At only 50 gallons, you're limited anyway.
Other dwarf cichlids might be alright, but keep in mind that rams and apistos both occupy the lower levels of the tank and may fight over territory. You need something that's passive and that occupies other levels of the tank. Keyholes and angelfish are only territorial when breeding and tend to stay busy amongst themselves if you get them in small groups, so they'd probably ignore your rams.