The 4 case fans (2 front, 2 back) have been removed. The 6" inline fan is doing all the work. It has a manual speed dial which I have been tweaking while Braiins OS autotunes. Trying to keep the chip temps below 75°C. A little disappointing, but basically having to run the fan at full power to keep up, so a little noisier than I'd like (~59dB @ 1m). But still way better than the high-pitched case fans. The S9 power supply (APW3++) has its own small fan, but it doesn't contribute anything audible when the 6" is pushing this hard.