Just overclock if you encounter low fps with your current CPU. Your GPU is already fast enough for 4x and perhaps even 6x res. Save your money for something else.
[color=#3366ff]CPU: Intel Core i7 4790K OC'ed @ 5GHz[/color]
[color=#339933]GPU: MSi N580 Lightning Extreme 3GB[/color]
[color=#cc3333]RAM: CORSAIR Vengeance Pro 16GB DDR3 @ 2666MHz[/color]
[color=#333333]HDD: Samsung 840 Pro SSD 512GB[/color]
[color=#6666ff]CPU cooler: Noctua NH-U14S w/Noctua NF-A15 PWM 140mm Premium[/color]
[color=#ff3333]MOBO: Asus Maximus VI Hero LGA 1150 Z87[/color]
[color=#cc3399]CASE: Thermaltake Urban T81 Full Tower[/color]
[color=#339933]GPU: MSi N580 Lightning Extreme 3GB[/color]
[color=#cc3333]RAM: CORSAIR Vengeance Pro 16GB DDR3 @ 2666MHz[/color]
[color=#333333]HDD: Samsung 840 Pro SSD 512GB[/color]
[color=#6666ff]CPU cooler: Noctua NH-U14S w/Noctua NF-A15 PWM 140mm Premium[/color]
[color=#ff3333]MOBO: Asus Maximus VI Hero LGA 1150 Z87[/color]
[color=#cc3399]CASE: Thermaltake Urban T81 Full Tower[/color]