Hi Gerry, thanks for looking at it.

Why are you mixing ac and dc servos?
I would like to use parts I already have (I'm missing Z and Y ball screws assemblies only).

What do you plan on doing with the encoders? You didn't mention if you'd be using Mach3 or UCCNC, but neither really does anything with encoders.
I should've put it differently: high pulse rates. Eg. Z motor generates 3000RPM x 10000ppr(4x2500) / 60s = 500kHz pulse rate is needed to spin the motor at highest RPM with highest resolution. UC400ETH should be able to handle 400kHz.