You're focusing on the wrong numbers. Those figures are about holding torque - how hard the motor holds still. This is not as important as how well it moves. That's determined by other things, like inductance (lower inductance means higher speeds without faulting) and voltage (more voltage makes a motor go faster, up to a certain point). The formula is: square root of the inductance times 32 equals optimum voltage to be supplied. So if you want the motor to go fast, you need to use a driver that will handle enough voltage, and give it an appropriate power supply. In practice, the sweet spot is around 50 volts for most NEMA 23 steppers, which works out to about 2.3 milliHenries of inductance. The running torque of a stepper depends on how much current it can handle. In a 23-frame motor, that will vary between about 2.5 to 4 amps per phase. But the inductance goes up along with amperage, so you have to balance all these factors. Look at the torque curves that should be listed with the motors to find one that maintains good torque at the speed you think you'll be running them, since torque falls off with speed, sometimes drastically.