Furthermore, how much of a difference is a 5800x3D going to make over my 5900x?
5800X3D is the best gaming CPU you can get for AM4. The actual improvement over your 5900X will vary based on different factors. Average FPS gains will vary based on resolution, GPU power, and settings used. In general, the better the GPU you have and the
lower the resolution you game at, the bigger the gains you will get over your 5900X. Conversely, with a mid-range GPU, 4K res, and all the eye-candy turned on, you might not see much improvement in average FPS. But 1% lows will be better, which means smoother frame rates and less stuttering.
The 5800X3D has been out for a while now, so buying one today really depends on how long you plan to keep your AM4 system. When it launched it was the best gaming CPU, bar none. Today, you can match 5800X3D performance with a ~$300 7700x on AM5, and the ~$200 7600x comes close. The IPC, MHz, and DDR5 gains of AM5 have negated some of the 5800X3D cache advantage. It's your money - upgrade today then upgrade again tomorrow if you want to like
Xexx
, but I suppose what matters is 1) if you are happy with your current CPU performance and 2) when you expect to make your next platform upgrade.