A bit over a week ago I got my 7900XTX stripped down and fitted an Alphacool water block. Very pleased with how it all looks now, image isn't quite the finished product, leds are all on default lighting as software wasn't running, and was still leak checking at the time.
However I have been having issues with very high hotspot temps. In certain loads I've seen it hit over 100ºC while the average core temp is ~50ºC. After some searching, soom found that a lot of people are having this issue on the XFX Merc 310 and the Alphacool water blocks. And the cure is to run a Kryosheet instead of thermal paste. So I have one of those coming tomorrow, and this evening I have drained the loop, stripped the card back down and cleaned it all up. I really hope this at least improves things!
I'll hopefully be back tomorrow with an update and a screenshot of nice low temps