The real property that matters in stepper motors is coil current. They have a rating for maximum coil current, which will generate the maximum heat that the motor can dissipate without failing. The voltage in question is the voltage that will, at steady state, generate that current (based on the winding resistance.)
However, when you step the motor, the inductance in the windings will prevent the current from immediately flowing. Thus, it is common to run the motors with higher voltage than "steady state" ratings, and have a controller that knows to chop the supply once the current has reached its desired target.
A 2010 single-start leadscrew will move 10 millimeters for one revolution, and the lever arm is 10 millimeters (half the diameter.) This means it will generate a force of (1 N.m / 10 mm) == 100 N. If the mass is 25 kg, it means you can accelerate at about 0.4g, which seems reasonable at first blush. You will need to tune the control curves for your stepper for this -- you cannot go from zero to full speed at once, as you need to take the inertia of the mass into account. Also, as waltr said, you need to allow for losses in the system.