Any water filter that takes out both minerals in particular "cacium" as well as chemical/biological impurities will do, when you are shopping around, take note as to what the filter does, and doesn't do. The mineral end is just to help eliminate deposits which can not only cause your equipment to break down, you lose overall volume and of course, have a residue that will create a bad taste. The rest is for taste, as a rule, if the water is bad, no matter how good your equipment you'll never get a superior cup of joe.
I couldn't agree more. Remember though when working with RO, most systems will waste up to 3 times the amount you get back. So for every 1 gallon of drinking water you wasted 2 to 3 gallons of water producing it. RO also doesn't conduct electricity well. So if you are using any type of machine that has a water level probe chances are it may or may not work. There are ways to getting around it but it just adds more cost to your water.