I am planning on getting the chassis and using an Arduino for the brains. Which motor controller would be good for those?
The most applicable motor controller is the TReX Jr, which will allow both serial control from your Arduino or RC control if you connect the motor controller to an RC receiver. You could also save some money and space by generating the motor control PWM yourself and getting just the dual MC33887 carrier. You could also use two TB6612 carriers, with the two outputs on each chip paralleled to give you the necessary current per motor.
If you do go with the motor-driver only route, make sure you have the I/O and hardware available to drive them (typically at least 3 I/O lines, including a PWM line, per channel).