Motor calculations? Help!

What calculations could I use to figure out the max voltage and
current specs on these motors? I am trying to figure out what
voltage to make the power supply and which drivers to get. I want to
have enough supply to run the motors up to the max rating of 2000
RPM, so I think the power supply has to be somewhere above 50V for
the Z axis motor and above 100 Volts for the X and Y going by the
back EMF that has to be overcome. I just don't know how much higher
or how to calculate it. Or I could even be way off base. Any help is
much appreciated. Please e-mail me at jevs@... if you have
any ideas. Here are the only motor specs, I had to pester Fanuc with
about 10 phone calls before they would even give me this. They are a
pain to get info from:

Fujitsu Fanuc LTD
Fanuc DC Motor 0 (z axis)
Type: 0-2000M
NO: D-771719
Date: 77 10
Permanent Magnet DC Servo Motor
Part Number A06B-0613-B031
Output Power: 0.4 KW (0.5 HP)
Rated Torque: 28 Kg-Cm
Max. Torque: 240 Kg-Cm
Max. Speed: 2000 Rpm
Rotor Inertia: 0.029 Kg-Cm-S 3
Back EMF Constant: 25 V/K RPM
Torque Constant: 2.44 Kg-Cm/Amp
Mechanical Time Constant: 25 mSec
Thermal Time Constant: 50 Min
Weight: 12 Kg

Fujitsu Fanuc LTD
Fanuc DC Motor 5 (x,y axis)
Type: 0-2000M
NO: D-771719
Date: 77 10
Permanent Magnet DC Servo Motor
Part Number A06B-0614-B031
Output Power: 0.8 KW (1 HP)
Rated Torque: 55 Kg-Cm
Max. Torque: 480 Kg-Cm
Max. Speed: 2000 Rpm
Rotor Inertia: 0.05 Kg-Cm-S 3
Back EMF Constant: 50 V/K RPM
Torque Constant: 4.87 Kg-Cm/Amp
Mechanical Time Constant: 15 mSec
Thermal Time Constant: 55 Min
Weight: 16 Kg

Thanks