6GB is fine for 99% of games.
Generally the OS and background tasks take 1-2GB, and the game itself wants 4GB. That will change as more games become 64-bit, but for now you're unlikely to see a significant performance difference from 6 to 8.
Should be enough , still 8Gb ram will become mainstream pretty soon enough.
So be prepared , that gtx 770 is a rock solid card should serve you well for a couple of years.
6GB should be fine with most games, 8GB is basically the current entry level standard, most prebuilt systems are now including 8, but many still at 6GB
6GB is fine for 99% of games.
Generally the OS and background tasks take 1-2GB, and the game itself wants 4GB. That will change as more games become 64-bit, but for now you're unlikely to see a significant performance difference from 6 to 8.