I really like the motor shield from adafruit industries. It is simple and it allows me to plug it in and start playing quickly. I usually have giant machines in my head, and the shield just wasn’t designed for those kind of motors.
You aren’t going to end up running your prius off of one of these controllers, but it turns out that you can almost double the max motor current draw just by soldering on some chips.
From Adafruit’s forums I figured out what ic’s I need to order (L293). Here is the label on the esd bag.
Now all that you need to do is solder them on top of the existing motor driver chips! As strange as it sounds, the theory has been vetted. Each one of those drivers can handle 600mA continuous. By stacking one on top of another they each handle ~600mA and you end up with ~1200mA! The motor shield has two driver ICs mounted on it, they are the two outer ones.
Here is a shot of the board. It is assembled, but it only has one motor driver chip per channel (‘channel’ feels weird there, but you know what I mean)