Actually the best i7 of today is only about 25% better in passmark single core test (graph), and since the physics+AI runs on single core, that's what matters. Intel is basically still using a tweaked Skylake architecture originally released in 2015, so your 4th gen i7 isn't bad at all by today's standards. If you had bought the i7 4790K you would be even better off, only 13% behind the latest and greatest Intel CPU. The next gen Ryzen 3 series coming in summer will hopefully provide a bump in both core count and single core. I think people are often upgrading their CPU for no good reason because they got used to the idea that a CPU released two years later is about twice as powerful as the old one. I think the main innovations have to be software-driven from here on because there is no "free lunch" anymore for software developers since Moore's law is dead.