i) What kind of FPS are you aiming for? 60 or 120?
ii) When are you willing to upgrade again? (i.e., can you upgrade CPU/GPU within a year or less if the new console ports require it?)For 60FPS at 1080p
If what eXXon said is true that the 930 wont bottleneck even 2 780s, get a 780 and save the rest of the money for later upgrades. In doing this, you dont have to worry about the 2GB VRAM limits or SLI issues of 770 SLI and you will still get 60FPS at 1080p, considering that you are willing to drop AA a bit (for example, to 2x SSAA in Metro Last Light).
If the 930 does prove to be holding back a single 780 (or in case you want to change your system), then get a LGA1155 system with a 2500K and overclock it to 5GHz. It should be a really cheap upgrade and will get you performance similar to Haswell level (probably even more at 5GHz).For 120FPS at 1080p
Since 2 780s will be way out of budget (seeing that 2 770s already cost $1182), get two 2GB 770s. I agree with BiG StroOnZ that more than 2GB wont really help and it has been proven by tech websites for the 6x0 cards (which is what a 770 actually is). Using a Titan, I myself have never seen the VRAM usage go near the 2GB mark at settings that my system can produce near 60FPS at. According to this
benchmark, 770 SLI will get 55FPS at 1440p meaning that it will get 98FPS at 1080p (applying unitary method). So it will do well in keeping the FPS near to that 120FPS mark, if not exceeding it at most times. And this is before the cards are overclocked.Why I'm suggesting a 780 over a Titan
: Much lower price, the performance difference between the two being imperceptible, and the 780 being easier to overclock. Read this
for more info on the last point.Why I'm suggesting 2GB over 4GB
: You wont be able to use the whole 2GB since the card wont get 60FPS at the settings that need the 2GB. Even when SLIed, you'll probably have to run the same settings since you're targeting double the FPS. The 2GB VRAM recommendation is without taking into account the requirements of console ports though. Almost nothing can be said about those since they havent been released yet.
Hope this helps!