The best CPU for your board would be an i7-3770. If you're up to changing entire platforms, then a cheap alternative is an intel Xeon E3 1231 v3 CPU, or the i7-4790S.
If you're sticking with your current board and not interested in overclocking, the 3770 should be cheaper than the 3770K.
If you're upgrading your board and not overclocking, the above Xeon and 4790S are good ideas. If you are overclocking, the 4790K is a good, more expensive alternative that can give some extreme power if set correctly.
I personally suggest keeping your current board and waiting until Skylake and AMD's ZEN processors are out before changing platform.
The GTX 750Ti is a great card for around $120 USD, and I definitely suggest it for a low-cost upgrade. It's fine for DayZ, which quickly runs into CPU bottlenecks left and right before taking advantage of hugely powerful GPUs.