jackrae:
by a "chopper controller" do you mean a PWM.
No, I mean something with an "onboard current regulator" or a "constant current drive".
jackrae:
but why are you using a chopper on a stepper.
Because wikipedia says I should. 
Stepper motor - Wikipedia
The higher the volts, the more torque and thus rpm. I want it to turn really fast, so this is one way of accomplishing that.