Caporegime
That looks an interesting option, particularly as it’s just a straight CPU swap. Doesn’t look like it matters that much for higher res though. I might be better off binning the new CPU idea and going for a 4000 series graphics card.
At 4K you're more GPU bound, the GPU is doing more of the work so the CPU becomes less important, but if you upgrade to a faster GPU then the CPU matters more again, it can be to such an extent that the GPU upgrade sees little if any benefit due to the CPU holding it back.