Thanks Hood,
Just to add a bit. For any machine being driven by Size 23 motors, the G540 is arguably the best value for money. Coupled with a 48Vdc 7A switch mode power supply, you have a complete 4 axis setup.
The G540 contains 4 separate G250 stepper drives that are user replaceable. If one blows it is easily changed. I've been using a G540 since they were first released, some 2 years ago without any issues.
Cheers,
Peter.