i5 4690 would be fine with GTX 1060. Although as GTX 1070 performs better than Titan X and i5 4690 cant be overclocked and it does bottleneck Titan X a little then it will also bottleneck a GTX 1070. Thats why people say to never buy a locked version of CPU while unlocked version is available.
Although GTX 1060 should perform around GTX 980-980ti and it will surely able to serve your needs.