Stepper motor driver
You do not need a "controller" to drive a stepper motor. All you need is a couple of transistors.
I've been driving these things just fine using an opto-isolator and a power transistor hooked up directly to my printer port since way back in 1986, and it still works today.
Personally - I think the idea of using a stepper driver is really silly. You don't need 2 computers and two sets of everything just to energize coils in sequneces! Worse - the fact that you've stuck another gadget between your computer and the stepper means that you've doubled the complexity of your computer code, and halved the useful info you can get back all at once. Yes - it's 400% sillier to use a driver, than to simply drive it direct from your PC!
One major thing lacking from drivers, is the PCs ability to measure the current the stepper is drawing. Without the driver, it's a simple matter to let the PC get this extra bit of info, and then your code can calculate the force that your steppers are experiencing - so you could for example detect a stall, or make them go faster when they're under less load, etc etc.