If you want a up to date cpu then you have no choice but to upgrade everything at once. Your platform is obsolete and has been replaced by the Ryzen platform specced above which is much more powerful than the FX series. You could drop in one of the more powerful FX series cpu's but from a quick Google your motherboard has problems with the vrm's overloading when a FX8000 series cpu is used. That only leaves the FX6000 series such as the FX6300 (£80) and FX6350 (£90) which I am not sure is that much better than what you already have (certainly not the FX6300 anyway). To be honest I wouldn't want to spend any money on your current system as it's just so out of date due to AMD taking so long to get their act together and releasing uncompetitive cpu's on a outdated platform. Either bide your time with what you have as the cpu is a ok match for the gpu that you have, or bite the bullet and upgrade the cpu/motherboard/memory to Ryzen. The second build (Ryzen 1600) is the better one of the two and for a extra £30 you get a extra pair of cores so should last you longer. To recoup some cash you could sell your current cpu/motherboard/memory. The memory alone should get a decent chunk of cash.
