Keep in mind, you can buy a PC WITH a parallel port for less than the cost of a SmoothStepper. My last two (2.4GHz, 1Gbyte, etc., one HP, one Dell) each cost me under $100. A SmoothStepper is about $150, and does not fully support backlash compensation, which you will probably want if you're building a machine on a budget.
Regards,
ray L.