I found the following post: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1215675974/all
I was a little unclear on the outcome. Can the arduino output a 25khz PWM signal from 0 to 100% duty cycle? One of the responses to the question in that link mentioned that the resolution would not be very good.
Here is the pwm spec again:
PWM Frequency: Target frequency 25 kHz, acceptable operational range 21 kHz to 28 kHz
Maximum voltage for logic low: VIL = 0.8 V
Absolute maximum current sourced: Imax = 5 mA (short circuit current)
Absolute maximum voltage level: VMax = 5.25 V (open circuit voltage)