First, it is likely that the 1000 watt and 1500 watt motors are absolutely identical.
Second, just about any 1000 watt DD hub will easily handle 1500 watts.
What you really need is a controller which will supply more amps, and a temperature sensor for the motor itself. May need to look into additional cooling, which you can do for about one or two percent of what a Rohloff will cost you.
