Cool so based on soft side of things I would go with South Americans rather than Centrals which I think you will like anyway
240 litres is a really fun size if you wanted to stick with dwarfs Checkerboard Cichlids are really nice, Cupid Cichlids are fun, Laetacaras are some good options. Apistos could look really nice - a group of Panduro with a single male and a group of females would look good (males are steel blue with red fins, females are yellow with black panda markings). If you wanted to go a little bigger Krobia Xinguensis would be a good candidate (though quite rare). Any of the smaller Acaras like Blue or Yellow (Pulcher or Metae) would work. The smallest Geophagus species Geophagus Pindare would work (but again quite rare). Festivums are nice and a bit unusual compared to Angels as an upperwater cichlid - though there are some nice Angel species out there at the moment like Leopoldi and Santarem if the man made colours are not your thing.
Always important to remember that to get the most out of your cichlids you need to build a community around them with upperwater schooling fish like pencil fish to give them a bit of confidence and some 'dither' fish to spread aggression and distract them from each other. I like to use headstanders for this purpose Spotted Headstanders or Annostomus Ternetzi are good candidates for this size tank.
I'd really recommend getting a GH and KH test kit set as it is important information to know
Wills