Best Servo setup for mill/drill?

Can anyone inform me on what kind/type of servo motors are best for a
mill/drill (RF 45)? AC, DC type servo motors?? Did a little
searching, but still a tad unclear. Any good books on the subject?
Amazon.com came up emtpy for decent books on the subject.

I have a set of ball screws (adjustable preload type) that will be
installed soon. I want to have a manual provision also, and am
working on a hand brake design for the X and Y. Thinking about a belt
drive system. I have some stepper motors (~600 oz-in units) that I
picked up free, but it seems that servo's are the the way to go??

Jason