I would personally only upgrade the GPU at this point. While the FX series is 5 years old, it still does an okay job for the most part, and a simple overclock should alleviate any potential GPU bottlenecks should you decide to upgrade. With Zen and Kaby Lake just on the horizon it really doesn't make much sense to do a CPU upgrade yet in my opinion because upgrading to Haswell means you're still only going to be using DDR3, and upgrading Skylake means you have to pay the premium for the over priced chips. So I would just wait to see what happens to the market when Zen does finally launch later this year. That said, I do not feel like there is ever really a bad time to do a GPU upgrade because the performance gain will always be very noticeable, especially going from a $100 GPU to a $250 to $400 GPU. I would personally recommend the R9 390 or GTX 970 based on what you're looking for. I lean more toward the 390 for various reasons, but mainly because it will undoubtedly age better due to having double the vram with double the BUS, significantly more shaders, and 5.1tflops of performance vs 3.5tflops. Plus the fact that you're running Linux and the Mantle based API Vulkan has just been released should, could, and probably will make for a significant performance gap between the two if and when developers start porting games to Linux using Vulkan.