I'd guess those stepper drivers date from the 90s, so there's every chance nobody remaining at Infotek who actually know anything about that age of machine.

I'd personally replace all the electronics and motors with more modern bits, as even more more modern steppers will give you a good boost in performance.
As for motion controller and software, take your pick.
I'd personally not use Mach 3 now, but if you have experience with it, it's as good a reason as any to use it.