What’s the most cost-effective way to upgrade my 2016 gaming PC?

I upgraded from a 6700K and GTX 1070 myself. Moving to a newer GPU helped a lot with graphics quality, but the old processor caused noticeable stuttering. Switching to a B550 board and Ryzen 7 5800X made the system feel much smoother. For a budget-conscious German build, a used B550 board and AM4 X3D processor combined with a used RTX 3080-class card or newer model could offer much better value than buying the newest parts. I’d also strongly consider replacing the PSU if you move to a significantly more power-hungry GPU.

The high-end CPU and graphics card combination you listed is basically a full modern-platform build. Once you add an AM5 motherboard, DDR5 memory, and possibly a new power supply, the total can easily reach around €2,000 or more depending on German prices. It will perform very well, but it doesn’t match a minimum-cost upgrade goal. A complete AM5 system with a less expensive processor and a strong midrange GPU, or a used AM4 system with a newer GPU, would likely give you a better performance-per-euro result.

DDR4 and DDR5 aren’t interchangeable, and consumer motherboards generally support one type or the other rather than letting you upgrade between them later. A Ryzen 7 9800X3D requires an AM5 motherboard and DDR5 memory, so your current RAM cannot be reused with that build. If saving money is the priority, a used AM4 setup such as a Ryzen 7 5800X3D or a good-value Ryzen X3D chip with a B550 motherboard could still be a strong gaming upgrade. You could then put the remaining budget toward the graphics card.

For a completely new build, you can probably reuse the case and storage, but the motherboard, processor, memory, and likely the graphics card would need replacing. The 9800X3D is excellent, though it may be more CPU than you need if you’re targeting high-resolution gaming. A cheaper AM5 processor paired with DDR5, or a value-oriented AM4 upgrade, could leave more money for the GPU. Also check the power requirements of whichever graphics card you choose before reusing the 650W unit.

The simplest path is to decide whether you want the least expensive playable upgrade or a long-term new platform. For the former, keep the case and drives, replace the motherboard, CPU, and GPU with carefully chosen used parts, and check whether the PSU has the right connectors and enough capacity. For the latter, move to AM5 and DDR5 now rather than trying to preserve the old DDR4. Your existing hard drive can still be used for bulk storage, but newer games will load much better from one of the SSDs.