krishpants:
I'm prepared for my logic to be ripped to shreds, but it was just a thought I had.
Some stepper motor manufacturers publish graphs showing how the torque varies with speed. You could use the graph (for your motor or one like it) to see if the torque at 200 RPM is significantly more than 1.5 times the torque at 300 RPM.
Also keep in mind that gearing introduces friction losses. It may also introduce backlash which would not be acceptable if precision control is required.
Driving a stepper motor with a higher voltage should give more high-speed torque - subject to the voltage limit of the stepper driver.
If you tell us what you are trying to drive someone might be able to give you useful advice.