If you want performance, then this would be my pick:
CPU: Intel Core i5-4690K 3.5GHz Quad-Core Processor ($219.00 @ Amazon)
Motherboard: ASRock Z97 Extreme3 ATX LGA1150 Motherboard ($104.99 @ Newegg)
Total: $323.99
Actually not only mine, but any gamer's pick even over an i7. And that's the best value for money capable of running any latest title on high with 40-50 FPS with your card. Ultra can be messy but that'll be because of your GPU, not this CPU, but you can get upto 40+ FPS on BF4 as its very CPU intensive. It OCs very well too. 4.2GHz stable is not bad!
But if you're on a budget then:
CPU: Intel Core i5-4460 3.2GHz Quad-Core Processor ($182.79 @ NCIX US)
Motherboard: MSI Z97 PC MATE ATX LGA1150 Motherboard ($89.98 @ OutletPC)
Total: $272.77
Would be the pick. A solid CPU, non OCable but I included a Z series MoBo so that if you wish to OC with maybe a Broadwell in the future, then your MoBo shouldn't be a constraint. You can still save $10 by dropping to H97. I'd rather opt a Z though.
Your current card is fairly powerful, but there're games which require some really crazy graphics, so it might be a constraint there. But I'd say with any of those above combo, your PC would be a gamer's PC capable of running any latest title on decent settings. With i5 4690K, no doubt it'd be really powerful and future proof, CPU wise, for a couple of heavy gaming years.