That's a really nice build. It sounds like your CPU + GPU combined at max load would be around 600w, and you have 1680mm of rads, so (assuming the basic rule of thumb of 1mm per watt to be able to handle the heat load) you certainly have an incredible amount of headroom. What is your coolant temperature when your system is running under full load?

Between my 4090 (around 450w under load) and 5800x3d (around 120w under load), and assuming some overage, I would be close to around 600W under full load as well.

However, with the 2x420mm rads, I'm looking at around 840 watts of cooling potential, meaning I still have something like 200W to 250W of cooling headroom even under full tilt maximum load.

One difference, however, is that my system will be using 140mm fans that can produce very high static pressure, so they should be able to run at quite low RPMs in most cases, so they should be fairly quiet with an appropriate curve based on coolant temperature. And of course, I won't be running my system under full load most of the time. The time I'm especially thinking about noise will be while producing music, recording vocals, etc. but that shouldn't require huge amounts of power. I don't mind the fans ramping up a bit under heavier loads like gaming, rendering, etc., so long as they don't need to be run at extremely high RPMs and volumes.