The voltage rating on stepper motors is effectively the minimum voltage required to make them work. You can use higher voltages than the "rated" voltage through a stepper driver (the higher the voltage, the faster each "step" will be). With the Pololu (A498x) and TI (DRV 88xx) drivers, you actually need a voltage higher than the "rated" voltage of the stepper motor coils to get them to step at a reasonable speed. I personally try and select motors so that the rated voltage of the stepper driver is less than 1/3 of the supply voltage (so, for 12V, I use motors that are rated for 4V or less).
So you can run the Sanguinololu board off 12V no problem with those motors.
Note: The 1/3rd rule is not based on specific rule, it's just something that I've tested and found to work well as a basic "will it work" test.
So you can run the Sanguinololu board off 12V no problem with those motors.
Note: The 1/3rd rule is not based on specific rule, it's just something that I've tested and found to work well as a basic "will it work" test.