What RPM are you expecting to get with these motors?
I have not used steppers for a long time but I would say if you got 1000rpm you would be doing extremely well. At 10microsteps that would equate to 2,000,000 steps per min, so 33.333KHz which should be easily achievable on nearly any computer.
Losing torque due to microstepping is a new one on me but as said I havent used steppers for a long time and have forgotten the little I dd know about them.
Hood