I upgraded 2 boats to 9.3 in 2022, both have Z Box and both work great. Sunsetter LXI and Response LXI. My friend with a 90's Prostar 190 did the same install with Z Box.
You might not have a good return spring situation or maybe it's just a need of the new software. If you get it just for the quick lock in and much easier to change set speed - those 2 things alone are worth it