Hmm wouldn't mind using a drill motor, although they tend to get a bit noisy, plus are not easily available off the shelf (apart from replacement parts).

Steppers seem like an interesting idea that I keep coming back to, one can find some with rather high holding torques, which should mean rather high torques at low speeds as well (I'm guessing a loss of around 10-20% of torque at 200-300RPM). The problem with those is you need a controller and a power supply and I'm not so sure I can fit everything inside the box. I'm also tempted to go down this route as I'm planning to use a small stepper on the lead screw, so using steppers for both would solve all problems.

Oh yeah, forgot, this is indeed for grinding coffee, Jonathan is right, although it might sound like a joke.

Regards,
dsc.