raptorb :
I buy computer for video editing. Did it worth it to pay extra and buy a gtx 780 or save money and buy gtx 770?
An i7 4790K would be your best bet. It's priced similarly to the i7 4770k. It's the haswell refresh that includes the fixes for high temperatures and voltage failures. The cpu is the most important part for rendering. Plus these GPUs are for gaming and you wouldn't notice a significant impact on heavy rendering performance. To notice any kind of jump you would have to get a GTX TITAN, which appears to be out of your budget. Or a Quadro or Tesla, which you might not want as you are asking about gaming cards.
Bottom line, if you're on an i5 or an FX 8350 and below, the hyperthreading in the i7 would give you much better performance than a GPU in rendering.
1. This is because the i5 doesn't have hyper-threading and i7 will encode %20 faster
2. The FX 8350 is a gaming oriented CPU and may beat the i7 in AMD optimized games but will be outclassed when it comes to production due to Intel's more efficient instruction set, and the way software tends to lean towards Intel technology.
http://images.anandtech.com/graphs/graph7255/57911.png
Just one example of the i7 transcoding. It goes like this pretty much for the rest of the benchmarks.