I have a manual Hardinge lathe I am retrofitting to CNC and I was wondering if the Galil plug-in would be a better option than the GRex. I intend on using some Yaskawa Servos/Drives I have. To use these with the GRex I would need to use a converter to go from step/dir to analogue. Could the Galil interface directly with them? I haven't seen detailed specs on the galil so I am not too sure of the inputs/outputs it accepts. Does it support analogue and MPG inputs? If not, I guess I could use a ModIO board for these.

The Galil controllers have ste/dir and analogue output.  Galil will interface to any servo drive.  It does have aux. encoder input, but not sure if the plugin for Mach has support for it.  Depending on the card you get you can have ~64 I/O.  I pretty sure they have plenty analogue inputs also.