If you have the cash, the 4790K and new mobo if you need those. Otherwise, the 4690K will be enough and it's the same socket as the 4790K. Your 770 is still a very good card and it might not be worth going to the 970 or 980 just yet.
If you have the cash, the 4790K and new mobo if you need those. Otherwise, the 4690K will be enough and it's the same socket as the 4790K. Your 770 is still a very good card and it might not be worth going to the 970 or 980 just yet.
I wouldn't upgrade your processor just yet. Are you primarily gaming, or do you do other things with this tower as well?
The advantages gained by switching from a 2600K or 2700K to a consumer 4th gen i7 are minimal. If you went the X99 route and got a 5820K that'd be another story, and there'd be rendering gains to speak of. And a small performance gain in terms of single core progression.
GPU I'd consider upgrading now, as you're working with a card that's literally living it's last days as the minimum for maxing out 1080p. Very soon you'll wish you had a single 290/780/970. I'd personally skip the processor upgrade til next generation and just get a GTX 970, or wait a small while longer and get an R9-380X when it releases
If you feel the need, I'd get the 970. I'd wait a gen or two prior to upgrading the Sandy Bridge setup to see a real difference. Sandy Bridge is still good and still relevant.