prit87 :
Performance wise i7 4770k is weaker than the i7 4790k the 4790k has 500 mhz of more default clock speed and its a haswel refresh processor so better cooling & more overclocking.
But there is no meaning of upgrading from i7 4770k to i7 4790k in gaming you will barely notice any difference.
I've updated my PC Picker page if you'd want to check it out, I meant to have the noctua D15 there. I've already got the 4770K, 840 Evo, G.Skill Ripjaws X RAM. I just got paid and I've got $400. I can buy anything, I was thinking the GPU would be the biggest upgrade, but I really hate to put it in my crummy Z87-G43 motherboard, also without my new PSU. What do you think I should buy first?