That water is very similar to the water in my city. It has been ion-exchange softened. It is NOT suitable for any brewing usage. The sodium and chloride are very high and the alkalinity is crazy high. The great thing about that water is that it is an excellent feedwater for a RO machine. The membrane should have a good long life since the Ca and Mg are so low.
There is not really a firm answer for 'best' RO system. The minimum you need is 3 stages: particulate filter, activated carbon filter, and RO membrane. Adding additional stages like an extra particulate filter or post-membrane activated carbon filter is unnecessary. I do recommend avoiding proprietary equipment like Whirlpool or GE since that might lock you into buying their replacement filters at higher cost. Since most of the equipment is fairly standard and all components tend to come from the same sources, the most important thing is the quality of the filters and membrane. Filmtec membranes are very reputable. Beyond that recommendation, look for a decent price. The other important consideration is how you will be storing your RO water. You can either keep it in an open tank and use a float valve to shut off the system when the tank is full. Or you can use a pressurized tank. In either case, you need a large tank capacity since RO output flow rates are low. If using an open tank, its capacity should be equal to the mash plus sparging water volume. If using a pressure tank, the tank volume has to be double the mash plus sparging volume since their is a big air bladder in there that reduces the tank's effective volume.
