First you say it uses steppers and afterwards you mention encoders and gecko 320.
Steppers do not necessarily need encoders and G320 is a servo driver AFAIK.
Anyway here are some basics: STEPPERS you mentioned based on the torque need anything from 24 to 70V and at least 20A to move properly, SERVO motors would need anything from 40 to 200 V and 10 to 30 A.
This is just a rough estimate and do not use this info before narrowing down what you really need. Check again what type of motors you have and what drivers you are planing on using, and let us know.