Building yourself may take a little longer but should save a little money. I got my GPU a couple months after my initial build. The nice thing is, you get to see how much impact the GPU actually has.
I had a 13900k paired with my old 3080ti for a while. The CPU was a nice bump & the 4090 took it to Smoothville.
(If you’re going to spend the money, go ahead and get a 13900k & 4090.)