Motor PWM Controllers Too Good to be True
I'm not sure the one you found will be easy to interface with an Arduino as it is obviously controlled with a potentiometer.

If you want to go on the cheap road, you should have a look at ESC for RC models. Brushed motor versions are rare as everyone uses brushless motors now, but you can still find a few of them. They are controlled with a ~30Hz PWM which is easy to produce with your Arduino, it's just like controlling a servo: http://playground.arduino.cc/Learning/SingleServoExample