I use a very simple two stage Spectra Pure and end up with water at 15 ppms. I use it for my plants and my fish. It does 50 gpd which is plenty. Lose your "water softener" for your RO system.....it's pretty pointless.

I don't use a DI system; I asked about it when I bought the system and was told it was better just to use the RO system for my needs.

PS...I dont' drink the water so that may make a difference with the DI.