Worth it for Resale? No. You won't break even with the base PPSG either.
You won't notice the difference with the z-box, don't bother. The z-box is designed for people who are on private lakes and ski tournaments a lot (i.e. constantly switching between Zero Off and PPSG). I would not consider it on my boat unless we moved to a private lake with more controlled conditions.
PPSG will be a huge relief to your wife and you. It helped my wife learn to drive without stressing our marriage too much.
94 Prostar 190, LT-1, Powerslot [SOLD]