Hi,
Any mid / mid-high ones...?
Is your issue with the cost, or do you feel that your CPU will bottleneck them? Except in specific games and especially after an overclock, a 2500K will not be the bottleneck even with a high-end card if you overclock. In the games you mentioned, either you won't have a bottleneck, or both the CPU and GPU will be bottlenecks. I agree with the 280X suggestion. GTX 770 is a good one as well.
That board only has a 4+1 power setup so I'd stay in the 4.3-4.5ghz range which should be pretty easy to achieve. TPU seemed to have no problem with overclocking.
http://www.techpowerup.com/reviews/Biostar/TZ68A_PLUS/12.html
280x seems like it would suit you pretty well, the 770 is a great card but you really want the 4gb model at this point and that puts the price much closer to a R9 290. I'm assuming a monitor upgrade is in your future sometime during the cards lifetime.
Edit: What would you like some links to? Sorry didn't follow.
Some board specific info here > http://forums.anandtech.com/showthread.php?t=2177995&page=1
Any general 2500k overclocking guide will tell you most of what you need to know.
http://www.overclock.net/t/968053/o...voltages-temps-bios-templates-inc-spreadsheet
^^Has some good general information about testing for stability etc.
We are getting off topic for VC&G though, maybe start a new thread if you need some more overclocking advice, be happy to help.
I have an i5 2500K overclocked to 4.5GHz using a piddly 1.275v at full-load on an Asus Pz68-V\GEN3 Sanday Bridge mobo. It only cost me $119.99 new 3 years ago. Why buy an 'K' series i5 and then buy a motherboard that can't overclock it? You only buy a 'K' series TO overclock it! It increases the lifespan of the i5 2500K by many, many years!