Is an RTX 5080 a worthwhile upgrade for a 5120×2160 OLED monitor?

The Astral 5080 should work well, but the premium models can cost dramatically more than other 5080 versions while performing almost identically. Unless you specifically want that cooler or design, a cheaper 5080—or a sensibly priced used 4080 Super—would offer better value. Your RM1000x should be enough, assuming the required power connector and cable setup are handled correctly.

At this resolution, even a 4090 or 5090 may struggle to run the newest ray-traced or path-traced games at native resolution with everything maxed. Expect to use DLSS or another upscaler, and possibly frame generation. A card such as the RX 9070 XT could provide a meaningful improvement over the 3080 Ti for substantially less money, especially if you mainly care about rasterized performance, but Nvidia remains preferable if ray tracing, path tracing, or DLSS features are important.

I wouldn’t rebuild the whole computer solely for this monitor. An AM5 upgrade would provide little benefit in games where the GPU is already struggling to render more than 11 million pixels. Put the budget toward the strongest graphics card you can get at a reasonable price, and consider waiting for a future high-end generation if the current cards still require heavy upscaling.

The 5900X, motherboard, memory, case, and 1000W power supply are still perfectly capable. At 5120×2160, the graphics card will usually be the limiting component rather than the CPU, so you don’t need to move to AM5 just to support a faster GPU. I’d test the 3080 Ti first, though—depending on the games and settings, it may still be usable with upscaling.