You could probably get away with smaller motors but depends on what you are gearing them I suppose.
You will need a power supply, you can make one quite easily out of a transformer a capacitor and a rectifier. Bob Campbell has a good pdf on this, see here
http://campbelldesigns.com/files/power-supply-part-1.pdf You will also need a breakout board, some drives and some limit switches. I like Gecko drives for steppers, have tried some others but the Geckos are way ahead of the others I tried. Then again the other ones I tried were cheap crap so ........
Limit switches can be of many types but if you want accurate homing then optical ones are good. Its easy enough to make your own optical limits up, bit of work if you use coolant as you will need to make a case for them that is waterproof but if you dont use coolant then just some shields should do.
Hood