oh, and nigel... by the way, generally with steppers you do NOT want to use wirewound resistors.
the whole point of using a higher voltage with a series resistance is that it increases the REAL component of the total impedance, so the load looks more like a resistor and less like an inductor. the reason for using higher voltage is to get current flowing through the inductive coil of the motor more quickly... by using a wirewound resistor you are adding to the resistance AND the inductance, so you won't get much of an improvement (of course, the resistor will have lower inductance than the motor coil so it will have some improvement, but still, it does defeat the point to some degree)