Other than what I already had in mind to potentially do I like the Argentea and the Gulper Cat. There were a few other good ones as well but those stand out. If I go with either of those It's going to have to be an online buy probably. I've never seen them available in my area. I work at an LFS and have not had either of these on my list of availables.
If my jd pair wasnt going into my 75 soon. It would be deffenitly be a female festae if i could even find one. i looked for over a year to get one and gave up before. Or second to that would be a pike cichlid i really love the cobra females when full grown
A couple things I would recommend...
Gulper Cat
Liosomadoras oncinus - Jaguar Catfish
Paratilapia bleekeri "Big Spot"- I love mine!!!
Tilapia Buttikoferi
Fossorochromis rostratus
Aristochromis christyi
Serranochromis - (Might be too big)
Aethiomastacembelus ellipsifer - Tanganyikan Spiny Eel
Caecomastacembelus plagiostomus - Tanganyikan Eel