I'm not a gamer but if i was the i5-760 and the better gfx card would be the route i would choose - 'if' you couldn't afford to upgrade the 2500k with a better gfx card in the near furure.
I think you will get more benefit from a 4 core chip coupled with a better gfx card rather than just the latest 4 core with an aging 5830 - BUT...
...havng said that - the 2500K is great value for performance (clocking potential), and if you think you may be able to upgrade your gfx card later on, using the 2500k, in the near future then the 2500K would the upgrade to consider...
Depends on future funds...