I'm running Nema 23 / 3Nm steppers driving 2005 ballscrews up to 1000 RPM via 1-1 belt drive giving 5m/min rapids. I use x8 microsteps and it all works fine. General opinion is that somewhere around x8 is the sweet spot between smoother, quieter, motion and losing torque (which happens as you wind up the microsteps). I wouldn't exactly say that my machine purrs but it isn't a bag of nails either!