Did you mean that you're going to replace your Jandy 3 way diverter valve or a sand/de filter multiport valve? Your current Jandy 1.5" valve should also accept a 2" coupling on the outside of the valve for connection to your new 2" pipes, eliminating the need for a new valve. Just cut the old 1.5" pipe flush with the valve. If you're a good plumber, you can peel off the old 1.5" pipe remnant, but that's another post.
I don't think you're going to gain significant flow rates but you will gain some efficiencies by going to the 2" pipes. Your pump will run cooler too, which helps to extend the motor life.