Devil's advocate....but you've got a very nice 4k panel. At 4K your CPU isn't going to be nearly as much of a bottleneck as it would be at lower resolutions. You could probably go high end last gen, 6900XT, 3080/Ti/90/Ti and things would be acceptable then work on upgrading the rest of your system.
I took the reference backplate off, but from what I've seen repasting is not only a PITA but not huge improvements. My temps on the 6800XT BE haven't really been an issue, though, with some aggressive fan curves.
I have a huge undervolt, I actually didn't save my exact settings from my best run, but it was @ 1050mV or so. Playing with voltage is the where most dividends came from. My card can hit 2.8ghz but will thermal throtlle, but it'll run 2.5-2.6ghz no problem on a full benchmark without thermal...
I upped power just a bit on my 6800XT to get the 22k score. 298 watts @ max draw. It's an AMD reference black edition card, and while the fans are....not quiet....at those settings the temps are within reason. I don't keep my card pegged at that extreme OC, but I'll game all day with a pretty...
Ran again because I didn't take a snip of the graph.....and got a higher score....average clock 2,542 MHz. Not sure if I just hit the silicon lottery here or not....this is a 100% stock reference card, reference cooler. Only mod is removing the backplate.
I'm pretty sure I'm stuck on a power delivery wall. Not quite sure I want to mess with MPT though. Either way getting 3080Ti numbers on a card In paid $659 for is a good, good feeling.
Nobody knows how to assist you because nobody has ever done this. Literally everything could be damaged because lord knows what electrical pathways you connected that should never be connected.