It's amazing how adaptable cichlids are. A lot of the cichlid people I know locally just keep their fish in tap water. I raise discus and angelfish this way, and all my severums, festivums, keyholes, Laetacara, etc. are in this water. They're all growing, spawning, and showing great color and health. I know that softer, more acidic water would be ideal, but I have no way to produce and store enough R/O water for all my tanks.
The biggest thing with rams, at least in my opinion, is keeping your parameters constant. They stress easily if things fluctuate too much.
I've never kept or bred firemouths, so I can't help you there.