Stepper Drivers and Motor sizes

I have been having a lot of fun writing motion software for my Arrick Stepper controller (Thanks Dennis!). Interestingly, I have found the 32-bit Visual Basic software I have written so far to be every bit as fast and smooth as the provided DOS software.

Anyway, the system normally uses 4.0 amp, 3v Unipolar NEMA 34 motors. From my research, am I correct in stating that Step motor drivers are constant current supplies, and that if I use a dinky little stepper that I risk burning it up? How careful must I be in matching motors to this driver? I would like to use a pair of smaller, NEMA 23 motors for my special application.

On another note, the prices of unregulated DC supplies in the 40V 5A range are scary. Are there any special considerations to "rolling your own?" It would seem a worthwhile project to save some $$.

Thanks gang!

Kurt