I'm surprised it's only a 4pin, I thought most were now 8pin. I know my GB board is 8 pin as I had to replace the PSU to match that exact issue.
As for the WD Green, even though it is only a data drive, don't expect great results from it as they are "green" for a reason. You would have been better with blue or even better black. Better again an Hitachi.
System looks decent enough anyway, hope you have lots of fun hours with it mate. I recently upgraded mine to i7 2600k and loving it but need to get a better cooler as Auto Gordian Knot rapes the cpu still and generates a fair amount of heat.