Stepper/Driver Advice (I'm new, but have done some research.)

[James Newton]

It's a bit late I guess, but I'd like to suggest the linistepper:
linistepper.com as a low cost alternative for students and hobby builders. It's unipolar, can manage up to 2 amps (3 amps max with CPU fans) at 35 volts and it costs $30 each in sets of 3 or more as a kit you assemble. Pretty easy to put together, but more importantly, it's very forgiving and cheap / easy to repair if you fry a driver. And... It's totally open source.

Good luck!

[H500]

The only difference between 24 volt power supply and 36 volt power supply is that the motors will run faster with the 36volts.

Correct. Double the voltage and you double your speed.

But also, aren't the motors only rated for like 4volts? so why is the voltage so high??

Inductance. The current does not have enough time to reach 3 amps before the next step pulse arrives unless you have higher electrical pressure to force it through.

Everything else you said was correct.