I got my 3060 for like $325 with 12GB ram and it is quite fast. You should prioritize vram over clockspeed, as any speed gains are lost if you have to tile on the GPU.
There will be a new power supply too. It only counts, that it works without problems using ubuntu.
So there is no advantage in speed with 16GB cards? Assume that raw-files have 50MB. Years before I had problems with “tiling”.
At the moment I am thinking on a card with 8GB and DDR7.
I am using parts of my old pc, but everything which needs to be new will be new.
For sure I will buy a new CPU, but no idea which, probably from AMD, depends on the motherboard, which I choose. I have to think carefully about the features I really need.
You may have your reasons for wanting Nvidia, and then this is not an answer to your question, but I would suggest you also look into recent Intel Arc B-series GPUs. I have only tested B580 12GB and it performs very well. Uses 8-pin power connector and is of modest size. For me the big advantage was that all support (kernel module, OpenCL runtime) is already in standard Debian/Ubuntu distributions. No kernel module compiles (Nvidia), no repository to configure for OpenCL support (ROCm for AMD). Here is a comparison for B-series: