Grumble (Chris, You'll note that I like using nicknames),

System architecture is nowhere as important as more basic concepts at this point.

Basicly, you have a low current capable control (component 1) driving (component 2) a high current draw system (component 3):
component 1: the recv'r board in the tank, the PC in ddrake's picture, or your desired Artificial-Intelligence processor.
component 2: The DRIVER circuit ( an H-Bridge circuit for each motor.
component 3: the motors.

It gets infinitely more complicated from here.....
Your choice for component 1. The easiest solution is the supplied HL recvr board. possiblly more versitile, much more complicated, is a PIC processor interface to intrepret whatever type of input commands AND,,, the software to support it. And so on, and so on, and so on.....