Sizing servo motors for BP size mill

I am looking at possibly converting my Ahha mill to run brush servo
motors using the Gecko 340 drives. Ball screws are .200 pitch, will run
2:1 belt reduction.
Current stepper motors are older Sigma and I was told they are rated for
840 oz/in at 10 amps. They are presently running at 7.4 amps via
Compumotor drivers.

What in/lb range servo motors should I be looking for to offer a modest
increase over what I have now?
Also, a significant reason for looking into this is I do commercial
work. When interpolating radii and holes, as well as shallow angle
tapers, I get a visibly wavy cut. We're not taking much here. It's an
aesthetics issue here, there are just classes of work where this is not
acceptable and thus I lose out on the work.
Will the Gecko drivers with a high resolution encoder improve upon this
finish?
(not looking for perfection, just a significant improvement)

Thanks,

Jon