The i7 3930k is by far the most useful cpu at 6c/12t but it's also a 130w lga2011 cpu so will require a very good cpu cooler (don't even think about budget cheapo coolers like hyper212) and an lga2011 motherboard, which aren't cheap and are getting harder to find.
For mainstream motherboards, the lga1155 i7-3770 would be better, even if it looses out a little to the i5-4670k in some games. It's getting to the point that 8 threads is more useful than 4 in many games, like WoW or gta:V or any other open world, high server drop games like fortnite.
What about grabbing the $50 200GE, a MSI or Gigabyte B450 board (for OCing the 200GE) and 2x4gb of 3000/3200mhz memory? This would be fairly cheap for a platform upgrade, the 200GE is decent @4ghz and could be a ok filler until the Ryzen 3rd gen series comes out then the Ryzen 3300 would be a solid upgrade (6C/12T and a higher boost speed then the 2600).
From op's choices, I'm assuming Indo-Asiatic markets where those older lga1155 systems are still prevalent on the used marketplace, you can even get new in box lga1155/lga1150 stuff. Also puts brand new tech at premium prices, including DDR4.