Controlling high rating DC motor
If you don't have much experience in building electronics, I recommend you to buy an already made driver. Pololu has a bunch of them, specially for DC motors: http://www.pololu.com/category/11/brushed-dc-motor-drivers

Anyway, I would like to know if the motor is a single-phase or a three-phase one, which application is it going to have... so I can help you further.