Do you know what the maximum amps your current controller can provide to the current motor. For instances if the controllers maximum is 25 amps @ 48 volts (25 x 48) the motor will get 1200 watts. Using that math to get the desired 1000 watts all your controller needs to provide is a little less than 21 amps.
Generally the controller will have a label that indicated the voltage range and maximum amps it can produce.