Contraptor set uses popular open source electronics: Arduino and Makerbot/Reprap Stepper Motor Driver in combination with Alltronics stepper motors. You can use your own NEMA23 motors and control electronics.
Wiring stepper boards
The diagram shows how to wire an axis with Electronics & motors subset. Since I/O pins are mapped to stepper boards in the firmware, it's not important which specific pins the boards are connected to. Just remember the sequence on the connections - STEP, DIR, ENABLE, MIN, MAX for Stepper Motor Driver v1.2. This might be different for other versions.
A generic PC power supply is used to power the stepper boards. Arduino is typically powered by USB bus. To use the PSU switch to turn it on/off, the green wire should be connected to any black wire on the PSU motherboard connector.