Bob, I understand your confusion, there is a lot to digest in a short time. I have been working with motion control systems for over 20 years and I am still learning. I would go here:
http://www.machsupport.com/software/plugins/ These are the devices that are supported by Mach3
The ''motion controller'' that you linked to above won't work in your application and it's not a motion controller. It's a USB interface device for Mach3 that outputs a
step and
direction signal for use with stepper motor drives. The 0-10V analog output is for the spindle VFD command signal only. There is also no provision for connecting encoders to that device.
A real motion controller uses a ''goto'' and speed input from the software and it does the trajectory planning and figures out the best way to handle that motion segment. Now in the case of Mach3/4, Mach actually does the trajectory planning, and sends out very short motion segments to the controller. Not my favorite way of doing things but it seems to work at milling machine speeds, not so much for high speed (not hobby class) routers as I found out. Mach4 may have fixed those problems.
In a Galil board you are looking for DMC-xxxx. The first two digits are the family (18xx, 20xx, 22xx, 40xx), the next digit is the number of axis. The last digit is the series. The 18 means it's a PCI card, a 17xx is a ISA Bus card. I haven't seen an ISA bus in a computer in years. All others are stand alone. An 1846 is the latest and greatest 4 axis PCI card. A 4040 is the top line stand alone 4 axis controller.
http://www.galil.com/motion-controllers look through the current and leagacy controllers. Anything with a 3 digit part number is not useful to you. If you decide on Galil from ebay, contact me before you spend any money.
So what to look for in motion controllers
Analog AXIS output +/- 10 Volt (many motion controllers have step and direction output also)
Encoder Input
Mach3/4 compatible
It doesn't have to do anything, but it would be a conversation starter
