There are lots of cichlids that could go in with the fish you currently have.
A pair of either bolivian rams (microgeophagus altispinosa) or blue/gold/german rams, Nannacara anomola (golden eyed dwarf cichlids), flag cichlids (Laetacara curviceps or L. dorsigera - the red breasted flag), and keyhole cichlids come to mind.
What are your water parameters like and what is the footprint of your tank? Match your water and tank size to the above fish (all would do well in the standard 20 high footprint (24"x12"), so water parameters are the biggest question.
Eric