Fire mouths would be amazing in that big of a tank you could breed them if you want or make a community of average sized new worlds like
1- Blue Acara
1- Severum or something haha.
Here a list of fish you should take a look at thought they are all new world
Green terrors are one of my faves
Jack Dempsey- Very colorful and get to a decent size
Firemouth- Colorful stay smaller have a mild temperament
Convict Cichlid- Aggressive small and pretty
Green Terror- Aggressive but gorgeous fish and are fun as heck to breed
Severum- Cool body shape mild temperament colorful
Blue Acara- Lolks like a terror but a lot less aggressive and gets a little bit smaller on the 6 inch side
Here's a pic of a green terror haha I highly recommend them!