Personally, I know for a fact that my benchmarks on my 4090 Gaming X Trio for hwbot are being held back by my 5900x. That I just got. There is a CPU bottleneck even with it boosting to 5150MHz in games and doing all-core loads at 4750MHz. But I think my wife agreed to this because I've never had an entirely new build (sans drives and a case and fans etc) at once, and also because she wants my current setup in her machine.
Two things I'm worried about for Ai Crystal: getting the thermal pad off of my NVMe drive since it has a metal heatsink with a thermal pad on it. Also, my board not having BIOS support for the chip so once I put it in I doubt it will post without me upgrading the BIOS using USB BIOS flashback. Also a little concerned about the board fitting underneath my rear fan, and my radiator pushing on or possibly blocked by the 8-pin EPS connectors. But my wife and I will figure it out and get it done. I really hope my AIO will fit and align with the screwholes. Also, getting this monster 4090 out of my case might be an issue, since it's a midtower, the rear screw thing for the GPU is like outside the back of the case and makes it difficult to remove GPUs (with my old 1080tis we had to use a pliers to bend the aluminum mounting bracket that the screws go in to be able to get them out of the case).
I love my machine and if the 7900x3d can boost higher for games (All I play really is Forza Horizon 4 and 5 and very occasionally but I plan on benchmarking them both before and after to see how much the extra cache improves the score), it can boost higher for benching, can do faster all core speeds for stuff like Cinebench, plus has up to 25% more performance from the extra L3 cache then it seems like a worthy upgrade to me. And I was planning on waiting for Zen 5 like ENTERPRISE but with this upgrade I'll have a good board and RAM for when Zen 5 drops in like 2026 or whenever. They supported AM4 for a long time, they will probably support AM5 too, and if I bought a 13900k I'd probably have to replace the motherboard when I want to upgrade. 13900k is on a dead platform and as usual Intel would require a whole new motherboard. I'd get way better scores in 3Dmark2001SE and 3Dmark2003 with Intel as Ryzen does terribly in those benches, but I can live without those globals.
And sorry if it seems like I'm hijacking your thread but we're getting or trying to get a similar setup. Maybe I should make my own thread.