hi, Brian, sorry for the long delay.
I'm completely new to cnc but i have a bit of electronic/electric knowledge,
I have the single board which can control 3 motors in 3-axis mode. Sounds like you have three individual single boards, but as i understand it, you can connect them up in series with the first board. It says to not re-connect the power to each board, only the first.
we followed the instructions that came with the driver board, seemed fairly straight forward, just check the motor wiring before you connect up because there's a few different ways of doing it for different motors.
Make sure you have a decent power supply, I used a 24v regulated supply, but when I was testing the motors with it, the maximum current when all three motors were running was about 1amp, so the driver boards are pretty good at not wasting power, so everything stays reasonably cool. Our motors are 2.4A per phase.
the mach 2 demo software works well, we haven't got a gantry built yet, but the motors work all the same.
if you get stuck with it let me know, the program is complex, but it starts to make sense once you use it.
i guess by now you've proabably got it all working and know more than me!
thanks,
aaron.