Uprading Prototrak Encoders??

Hello, I currently have a Clausing kondia FV-300 manual mill with 2 axis Prototrak A.G.E. 2 cnc control on it. It has the old style Trav-a-dial encoders on the table for feedback. Im thinking of upgrading the encoders to the Newall Linear encoders that are more accurate and protected from chips and oil. This upgrade though is pretty expensive. My question is. Is the money worth it? Im thinking of uprading to possibly a Mach4 based system in the future, but not sure how soon. does anyone know if id be needing these linear encoders with the Mach system as well? or just encoders on the servo motors. Im also thinking when i sell the Prototrak control i will recoup some of the money from the upgrade.
Any thoughts or opinions would be greatly appreciated.
Thanks, Scott