Ha, I was going to suggest a Del for you - still have the patterns but a bit more active than the Endlis. Congrats!! You could easily get a few more upper jaw polys if you wanted in a 120.
You might consider a Paratilapia Polleni for your mid-level swimmer, also from Africa. You'd need to be sure you didnt' get it at a bite-size and that it wasn't big enough to eat the albino Sens (who tend to grow more slowly.) Or you could do a few Ctenopoma Acutirostre (also be sure to get non-bite sized), also African. Butterfly fish would also work for the top level with the Cteno, not sure they would work with the Polleni.
Most of us feed our polys every other day. Definitely mix in some fish like silversides or tilapia, and then a good quality pellet. Carnivore or NLS are good. Massivore is a bit big for the smaller upper jaws and will need to be broken up and it is stinky.

I've also used sinking cichlid gold for variety. Then you can throw in shrimp/krill and some live blackworms or earthworms here and there for an even more well-rounded diet.
Supposedly feeding catfish once per week can help prevent bloat, which can happen with these guys, esp. the CB ones when they overeat. Rinse well and feed right before a WC because it will leave an oily film on the water surface though.
You want these guys to eat well but try and avoid a huge "beer gut."
Welcome to the poly crew!