I moved this thread here and deleted the other one.
6 angels will be a good start for a 55g. What else do you wish to keep there? You could try tetras but beware of some that will certainly end up eaten by your angels since angels can prove to be a menace to them. In the wild, angels can ambush their prey, most notably the neon tetras. Avoid fin nipping species such as well such as the serpae tetras. If you want tetras with your angels, cardinals, rummy nose, penguin, glass bloodfins, red phantoms, black phantoms, lemons, head-and-tail-light tetras, red-eye tetras and glowlights certainly fit the bill.
Others to consider are pencilfish, hatchetfish, corydoras, blue rams, Bolivian rams, keyhole cichlids and small species of plecos such as bristlenose plecos. If you don't mind non-South American species, kuhli loaches, rasboras, danios and a few species of barbs such as cherry barbs fit well.