It's a good GPU. It's just you asked if anything could be improved. For more performance as a mainly gaming rig, the GPU is the most important part (as long the other hardware can keep up, which in your case it can). So if you want to spent more money, spend it on the SSD and GPU.
If it was me personally i would improve the system with a Samsung Evo 840 pro SSD (i have it my elf) a slight better PSU (just because i am a fan of eco frendly stuff. I have a platinum PSU) and then a better GPU. But that's gonna cost a great deal more.
If it was me personally i would improve the system with a Samsung Evo 840 pro SSD (i have it my elf) a slight better PSU (just because i am a fan of eco frendly stuff. I have a platinum PSU) and then a better GPU. But that's gonna cost a great deal more.