Rags, if your planing to build them your self. Build a seperate base. The toe kick is about 3" above the floor. You can build a seperate toe kick out of PT or plastic 5/4. You can work the plastic with standard wood working tools then cover it in a veneer. That would give you the best of both worlds. Then switch to either cabinet ply or mdf for the cabinets them self.
I did that for one guys garage cabinets. Even if you use marine plywood. the bottoms will swell unless they are completly encapsulated in
epoxy or some other water barrier.