What motor controller do I need to drive two 200W motors?

I've been using two Pololu Simple Motor Controllers at 24V, each supposedly able to handle 12A, but they burn out every time I use them (usually when stopping, the motors are pulling about 300 pounds.)

Is there a better controller out there that is less than $100? and what size fuses should I include in the setup, to stop the controller before it blows?

Thanks!