Which case should i get?

Well since it's only a color difference it's really up to you. My opinion though is the black/blue model would look better, but its only a matter of personal preference for aesthetics.

I would tweak your build slightly and save some money on the Cpu. Drop down to the I5 4460 since you are paying 18 dollars more for the 4590 and it's only a 100mhz difference. Not noticeable at all, save the money.