Yes, soft water is easier on an RO/DI unit - especially here in SA. But, your incoming TDS is still very, very high, for reef inhabitants. Also yes, installing a water softener in a house not pre-plumbed can be anything from "not too bad" to "what was I thinking!".
If you have some patience, decent units do occasionally show up. But, most experiences show you will throw money at a used unit. Rarely do they show up with "just changed the membrane and filters!" in the ad!
Bill
215g FOWLR... and anemones, GSP, gorgonians... carp, that isn't FO!
"I killed my first SW Fish in 1971..."