I just upgraded two of the stepper motors from 0.3a 400-steps-per-turn to 1.2a 200-steps-per-turn.  It's a little less accurate and a lot more powerful.  Since the power at the wrist is 1/sqrt(length) I don't expect a big improvement.  Next step power-wise is to find gearboxes.  Next step overall is to get axies 4 and 5 installed.  I've got it worked out in my head.  Bevelled gears are a real challenge.