180g would be a great setup for 1 big American cichlid and an assortment of african cichlids.
You could get 1 big American cichlid of your choice, such as: oscar, devil, midas, trimac, flowerhorn, managuense (jaguar), salvini, jack dempsey, texas, red terror, blackbelt, green terror.. pretty much whatever big American your LFSes sell that you like best. Excludes dovii, umbees, and peacock bass.
Then you get about 15 african cichlids. Just about any african cichlids whatsoever. Try to make sure they're all of fairly-similar size, and avoid the Tropheus species.
You get a tank with a nice centerpiece "bruiser", and then 10-15 other smaller aggressive fish. The tank will feature constant activity as the africans battle one another for territory, and they'll all indulge in any small fish you choose to feed them.
here's a good guide to many of the more common african species out there
http://www.cichlid-forum.com/articles/species_profiles.php