My advice is to dump the servo's for AC brushless with Step/Dir drives and go with Centroid Acorn Controller.

The Centroid control Software is built proof tried tested over many years and comes with built-in conversational Cam.
The Controller is 4 Axis with Spindle encoder input and 0-10V analog Output for speed control. With more than enough I/O for Mill.
http://www.centroidcnc.com/centroid_...ontroller.html

You can buy AC Servo's cheap enough from China which will work fine. This combo will give you great machine with strong control that won't cost a fortune.