Stepper motors for mill/drill & source of supply?

Hi,

Can anyone recommend what size stepper motor I would need to drive a
mill/drill table for CNC control? I've heard numbers in the range of
400 oz.-in., but I'd like to hear from those with experience.

Also, where's a good source of supply for such a motor? It seems as
though there's quite a large price difference between the different
sites on the web.

Thanks,

Jeff