so you want us to do your homework for you!?
cpu - dual or quad intel or amd - for 3 wow accounts you could use a Dual core easily
atleast a 512 card - i've got one for sale for 100 bux Nvidia 7950 gt oc
power supply anything 500+ if you are running dual core and a beefy graphics... 650+ for a quadcore and beefy video card
motherboard - all up to what you want... Intel or AMD just dual or quad capable with pci - e slot 4 ram slottage
harddrives are cheap you can pick up some 500g sata drives for 90 bux.