honestly you could go up to a GTX1080 without much worry, there will be some titles where you will be held back by the CPU a bit (CPU heavy games, like BF1), but overall it'll perform great.
This being said... don't buy a 1080 and use it with a 1080p resolution monitor... .that'd be a waste.
If you are looking to pair a GPU with your 7600 for 1080p gaming, then you should just stick around GTX1060 or max 1070 (but the 1070 is a bit overkill for 1080p gaming as well, but it will last you longer)