reddevils and severums are way too big. angels can be pretty but from what i've read they definently can be tank bullies, and convicts of course are just as bad if not worse. If you want a community tank with SA cichlids go with some other more peace dwarfs cichlids. Rams would work, but they have a short lifespan (couple years?) and are sensitive to water. Bolivians seem to be a little better at adapting to non-perfect water conditions, and live longer. (they are also slightly larger-- 3 1/2 - 4''). You could probably do one pair of rams, a school of 6 medium-ish tetras, an ancistrus, and maybe even a few panda cories?
5 firemouths would be very bad news for a 55 come time when they decide to spawn, so i would go with 1 mated pair and provide lots of plants and hideaways.