HD PWM DC speed controller

I work with high school kids building robots. Most of the time, we
are us IFI Robotics controllers and Victor 884’s -
http://www.ifirobotics.com/rc.shtml to supply power to the motors.
However, we are now trying to make a unit that we ride, so we are
interested in replacing the whole remote control system with two PWM
motor speed controllers. We currently have two choices for ground
drive motors and their specs are thus: 12 vdc, 270 - 340 ish peak
watts, stall torque 350 â€" 570 oz-in, stall amps 96 â€" 133, no load
running amps 1 â€" 2.7 amps, no load rpm 2700 to 5300. I've looked some
for PWM controllers, but don't seem to find ones big enough. Any help
would be appreciated. thanks, Chuck