homer,
Camtonics sells controller kits.
You need to determine what your requirements will be. ie; steppers or servo motors ( maybe a combination ), the drives you will use, then the power supply required. I would recommend a power supply that is adequate for four motors at max amp rating. The controller box should provide enough room for easy installlation of all the parts. So take your time, think about the machines you have now and may have in the future, thus , buy / make once.
RICH