Need some upgrade advice for my 6 yrs old PC

I upgraded my card to an XFX RX480 a couple months ago but I feel like I might need to upgrade some things along with it. Currently I have:

i7-4790 @4.00 ghz

MSI Z97 PC Mate

Ballistix Sport 8GB DDR3

Corsair CX 600 PSU

Corsair H75 Liquid Cooling.

Samsung SSD 840 EVO 120GB/Samsung SSD 850 EVO 250GB

ZALMAN Z9 Mid Tower.

I don't care much about how the PC looks (just look at the picture I posted good lord) but having a somewhat cheap case that can have good cable management would be nice.

Budget is probably around 500-600$

Pics:

http://imgur.com/3aedFKK

http://imgur.com/aG7pE9R