I’m currently using an AMD 5950x and an Nvidia GeForce RTX 3080 LHR, pushing video to a Dell U4021QW, which is a 40" monitor running 5120x2160@60hz. A few of the games I play are pretty challenged at that resolution, so I’m thinking of upgrading at least the video card. Is there any reason to build a new system with a newer CPU as well?
High resolution will tend to hit the GPU and not the CPU. If your existing CPU is working fine for you, I’d probably leave it as-is.