Power supply for 1.7A stepper motors
Voltage is not mentioned in the motor datasheet because proper driving of stepper motors is done by controlling the current through their windings, not their voltage.

What is typically done is that you have a supply that must provide a voltage way higher than what is theoretically required (here 1.7Ohm * 1.5A = 2.55V), and you have a stepper driver that will chop this voltage before providing them to the windings, to ensure that the rated current (1.5A) is never exceeded. That will lead to a voltage across the windings that has a high peak at the beginning, and then decays to finally reach the steady state voltage. This way of driving the stepper will ensure best speed and torque performances.

In short: You can choose the voltage you want (higher is supposed to be better because it will drive the motors more easily, but stay within the specifications of the drivers you choose). Just ensure that the supply will be able to supply the peak current required a per the motor specifications.