Hello Terry,
If you are mining only with graphics cards then a top-of-the-line CPU is not really necessary, you will however want a Motherboard that can house multiple graphics cards or one that has many PCI-E 1x ports so you can use adapters such as these for connecting your Graphics cards to the PC for mining purposes.
Regarding your power supply, it’s really up to how many graphics cards the Power supply and support, if you want to run 4 x cards make sure the Power supply has support for 4 x Graphics cards.
Recommended Mining case / frame – Click here to see on Amazon
Let me know if you have any other questions.