The PWM outputs, like all Mach3 outputs when using the PP, are limited by the kernel frequency. The higher the output frequency, the less resolution you get. With a 25kHz kernel, and 10kHz PWM frequency, you'd have less than 2 bits of resolution. Some hardware motion controllers, like SmoothStepper, will allow higher frequencies, but I'd be surprised if even they supported 10 kHz.
Regards,
Ray L.