An under sink water chiller is a great addition to any reverse osmosis RO or filtered water system.  If you are using a RO reverse osmosis system you will need to pay attention to the materials used in the construction of the water contact surfaces.   The cooling system used on water fountains are generally copper lines.  Copper, many plastics and gasket materials cannot be used with reverse osmosis water.  RO water is so pure that it will "leach" particles from the copper, plasic, etc.   For this reason it is best to use a chiller that has a 100% stainless steel water pathway.