Further disassembly yielded a few interesting insights about the hardware.
The three stepper motors for X Y and Z axes are all within the range of the smoothieboard's output. 24V, 1.5A. The only challenge is that these motors are bipolar without center taps, so a little homework must be done to figure out which fields are coupled. This can be accomplished with a low voltage AC source, and probing the remaining field pairs looking for coupled AC voltage. With this information, we can correctly wire the stepper motor in bipolar series orientation.
The two motors for the extruder heads, however, are 8 wire servomotors. This presents a challenge with the smoothieboard, probably requiring a piece of hardware inserted before the stepper driver to take step and direction signal and convert that to the correct servo signal. If anyone has any suggestions as how to do this, I'm all ears.