dont get a merlin with your tds, it will eat resin. you dont need to produce water that quickly if you are using a static tank at home, a 300 gpd ro will be fine and would be even better with a booster pump.
i personally use about 300/400 ltrs a day, and i only use a boosted 200gpd ro-man unit, and that takes my tds down from 450, at the moment, to 4.