The power amp mods are all complete. I had to get a small buck converter to take the amp fan header voltage down from 24v to 12v to match the Noctua fan. Made a big improvement as the old fan was super loud.
I ended putting the low noise adapter on the fan, spins a bit slower but still puts good amount of air through. I don’t think this amp will be driven to the extent that more cooling will be required.