Is this a realistic accuracy???

Well as it turns out the stepper motors may not be used for this project after all... The test fixture requires the motors to rotate smoothly at very low rpm(2 rpm) and even with microstepping (1/16th step) the stepper motor does produce slight jerkiness. The said it looks like my only other options are: continuous rotation servo, or geared dc motor with encoder. Do you guys have any other suggestions what might work? Will a dc motor with an encoder produce smooth operation? Will a servo produce smoother rotation? Would it be possible to rotate a continuous rotating servo for over 1000 revolutions and not encounter problems and also be able to adjust speed and revolution number? I will continue to work with the steppers and power supply to see if I can get an even smoother rotation, however the product that we are trying to test has a tendency to amplify any type of choppiness in the rotation.

This is what I had in mind for the servo:

But my concern is that in order to count the number of revolutions I would have to use the RPM to calculate the total revolutions completed, which seems like it may not be particularly accurate, especially with 1000+ revolutions.

And this servo controller: