Hi,
the more I think on it the 4.5Nm, 2.5mH stepper above (34HP29-6004S) with 80VDC or 90VDC driving it will handily do 1000rpm and STILL retain half its torque, say 2.25Nm,
and may even do better, say 1250rpm or 1500rpm with still useful torque, approaching 2Nm.
If they were direct connected to 5mm pitch screws that would equate to rapids of 5000mm/min (1000rpm) to 7500mm/min (1500rpm), both of which are very respectable
in a smallish hobby machine and yet still have something like 5kN of thrust at low speed with a 5mm pitch screw of 16mm diameter.
I really do think this model motor is the hands down winner. Don't mess around with a small motor for the X and Y. If the larger 34 size motor will fit then bung them in there and let the fun begin!
Craig