The Ryzen 2600x is multiple times better than the Ryzen 3 1200, even with a good overclock. I would upgrade it. The 1060 is technically too "weak" for the 2600x, but you should still see a performance gain in gaming. If you have a big enough budget, I'd recommend upgrading to a 1070 if possible or even an upgrade to a 6GB version of the 1060 would see a good performance gain. But otherwise, yes, the CPU upgrade is overall the best choice you could make.