IMO it depends on your filtration. Do you have a good enough system that can handle the bioload of large fish like the angel, grouper and eel. If so my suggestion would be a bird wrasse of some king, an anthia, a maroon clown, or a yellow tang. Stay away from triggers, lionfish, butterflies and anything smaller than the anthia. Your filtration needs to be top notch with what you already have, but you do have room for one more fish.