RenzoRaptor :
Dear Textfield , I will be playing games like BF4 , CS:GO , TF2 and some graphically intensive games like Crysis , Tomb Raider and the Metro series.
At stock, the 780 is only about 24% faster than a stock 770, but that's due to the 770 having a much faster clock speed, even at stock. On OC, and sometimes you can find an OC 780 for the price of REF., that margin is much wider.
At identical clock speeds, the 780 is theoretically 50% faster than a 770 thanks to 50% more CUDA cores.
It all depends on what clock speeds your video card vendor gives you, then.
Given the kinds of games you play, and if you continue to wish to push heavy games, I would recommend an OC 780 for the best performance if you can afford it. My father bought an OC EVGA 780 for I think about $520, and it runs happily at over 1200 MHz, which puts it far past any 770 in performance.
Do you intend to ever go SLI? If so, you might want to look at cards with REF. coolers mainly, because those do better in cramped SLI configs.