I replaced my galley mixer tap this spring. I wanted a extendable spray head. Bought a Moen at the local home supply centre. Bought an inline filter at a hardware store. Filter is used a lot in RV's. you can choose the filter element required, chemical or sediment. Took a bit of fiddling with adapters but it works great. Old mixer came out easily and new one fit in the same hole. The total job cost under $300 for all parts. Only does the cold water. Would require a second filter for the hot water, which they don't recommend.
Doug