I assume you're comparing an i5 6400 and an i7 6700. The 6400 won't generally hold you back in all but the most CPU demanding titles. The 1060 would probably max out first otherwise. If it's a prebuilt system then go ahead with the 6400 and you shouldn't have any regrets. If you're putting it together yourself, check out the i5 6500, it's typically about $20 more than the 6400, but has a base clock of 3.2 GHz rather than 2.7 GHz.