We are stepper motor , driver and controller manufacture in China, may be I can provide some helpful information to you.
From your message, the stepper motor you have is NEMA 34, for this size stepper motor, the max speed a Chinese factory can do is about 1500rpm, but Nanotec stepper may reach 2000rpm.
But we almost never up speed to 1500rpm, right?
Also, you must have speed-toque curve, as you can see, it has stepper driver/current and microstep on the top of the curve, why? it because the chagnge of the toque is related to stepper driver, microstep and currrent.
You must to know clearly about how much speed and toque yo do need before choose a correct stepper motor,
For more question, you can contact my email :
rony@jugetek.com
I do not check forums message often.