You can get all male congos too, to be sure they'll be bigger and less likely lunch.
Another different thing to throw out there since you have a bunch of some eel shaped fish is an African Brown Knife fish. Cool looking, supposedly more active and out during the day, and smaller than the ghost knife. I have read from many people that the peacock eels are pretty shy and you often don't see them much. Might be nice to have a fish that is a different shape and visible?
I love the eel-shaped bottom fish too, so I totally get wanting a tank full of them. I'd be pretty happy with an 8 foot long shallow tank full of bichirs, ropes, eels, gobies, etc. LOL
Don't forget the sand substrate for your snakey guys, esp. the eels.
(And I am just going to put one more word out on the Ctenopoma. Mine is so cool. He is interactive, uses all areas of the tank, eats like a pig - literally anything - eats out of tweezers and pipettes, and his stalking/I-am-a-leaf behaviors are really fun to watch. He is captive bred, not sure if that makes a difference but he is always out and about. I do have a pretty densely planted tank though.)