a/c  motor speed control

I'd like to use the Arduino to control the speed a 650 watt router. The router has and input of 230v ~ 50 hz and a no load speed of 11500 to 32000 rpm. Ideally I'd like to control the speed from 4000 to 10000 rpm

I've been reading the post on dimming lights and understand the concept if not the detail.

Can anyone reccomend an appropriate kit where the 240v is plugged through the kit and the arduino is used instead of a potentiometer to control the motor speed?