If you need it to run on a microcontroller and you aren't an expert in a high level one I would suggest either a raspberry pi or a beaglebone black. Those could potentially handle voice recognition. Infact, since the beaglebone black runs linux or android, you may already have code examples to get you most of the way. They are both ready to run development boards, so you don't need to figure out as much about electronics or the development environment. As for running motors, if we're talking about DC or steppers, almost any microcontroller can do it.
