I cannot see how changing your steps per unit will affect your velocity, one is a distance, the other a speed.
The only way to change your velocity is, either get the motors to turn faster, or reduce or introduce step up gearing between the motors and the table (or cutter).
If you increase the gear ratio between the motor and table (or cutter) then your accuracy will suffer, in that each step will mean a move of greater distance. Your steps per unit seem an odd number anyhow at 15,245 how do you arrive at that.
As far as the motors turning faster is concerned, I take it you have altered the distance per minuter upwards and your motors are now complaining and will not turn any faster - are they steppers or servo's. I recently increased my steppers by a factor of 10 by rewiring, and you can also increase the voltage to get them to turn faster. Servos I don't know much about.
I don't know what you are trying to move - is it a gantry? Is it smooth enough to move at that speed. There will be a physical limit to the weight your motors can accelerate (and decelerate) - and it may be that your motors have reached their limit, and to move faster, larger motors will be necessary to get over the inertia.