Hello.
The Volt/Amp figure tell very little about the motor characteristics as it is a DC static value. Try finding about its torque and current. That is figures like 1600 oz-in 6Amps would be more meanngful.
Since you already have the driver I suggest you try it with a supply no more that 45V/5A. A linear supply consisting of a transformer, a couple of diodes, an electrolytic capacitor, a bleeder resistor and a fuse will suffice and be more economical than a corresponding SMPS.
Depending on the ratio of your speed reducer that amount turns into a multiplier, more or less, of the torque of the motor. Hence it´s ultimately dependant on your particular holding device and how that torque is applied to holding your workpiece.
Regards.