In this case, then upgrade the CPU for now. Then, wait until a future game needs a newer, more powerful GPU or your current GTX 1070 goes "legacy/obsolete" from Nvidia itself before you perform a GPU upgrade.Just 1080.. no big rush to go to 1440.. I personally couldn't tell a difference.. to my eyes 720, 1080, 1440 4k all look the same. But that's me. Not saying others can't see the difference.
If it's that huge of a price difference, then keep in mind that current games do not take full advantage of more than about eight threads. Therefore, the 3% performance difference is based on current games.Huge price difference from 3600 to 3700x. I can get a ryzen 5 3500 for less than $150 Usd , only 3% more performance with 3700x over 3600.. according to UserBenchmanks website. Not worth the price tag imo.. but thanks for input XD