Tony,

The Astrosyn steppers are OK and fine for a small router for wood, pcb, plastic but you might struggle with aluminium. You won't get more than 0.8Nm and 300rpm out of them on a unipolar driver. The size you have suggested is possible, will depend on the design. The power supply will depend on your driver... but you probably dont want to go above 12v. Depends on the current limit resistor (light bulb) you've used...