you can work it out easily actually. you know the torque you can get from the motor at a given speed (datasheet). You know the pitch of the ballscrews and their pitch diameter. With your gearing you can find out what the speed of rotation of the motor and the ballscrew need to be to get the speed you want. Then use the equation in page two of this: http://www.mech.utah.edu/~me7960/lec...lculations.pdf
select an efficiency of around 0.8 and you are good to go.