Watch Dogs requires an i7-4770k to play on ultra graphical settings, that's according to Game Debate. An i7 for any other games would be more than beyond adequate.
Therefore if you're not planning to overclock, I'd definitely consider the Intel Xeon E3-1230v3; which provides similar performance to an i7, but at a fraction of the cost, you may even find it cheaper than an i5-4670. You don't have to worry about this (since you have a GTX 680), but you should know that since Xeon's we're initially designed for servers, they don't have integrated graphics, hence you'll need a dedicated GPU to boot up your system.
Watch Dogs aside, an i5-4670k should be able to max out most games. With a k edition CPU (i5-4670
k) you should be overclocking it, as it was designed with an unlocked multiplier; hence you'll need a motherboard with the prefix "z" e.g. Z97.
Again if you're not looking to overclock, I'd go with an Xeon E3-1230v3, as stated which provides similar performance to an i7.
All the best.