Stepper motors' torque specs are based on current, not voltage. The voltage value is simply the current x winding resistance. The current you set in the driver is the average value that will be delivered to the motor. You should not have to drop the voltage from the driver/power supply. As long as you set the current within the motor's spec, and as long as the supply is rated for higher voltage than the motor, it will be OK.
With smaller, lower voltage motors it is common to run the motor at 8-20X the voltage rating of the motor.
With smaller, lower voltage motors it is common to run the motor at 8-20X the voltage rating of the motor.