There's a fairly straightforward set of engineering tradeoffs at play here. As written, use a water pump or make the case surprisingly big are solutions, using

There's a fairly straightforward set of engineering tradeoffs at play here. As written, use a water pump or make the case surprisingly big are solutions, using a power supply sufficiently oversized that it doesn't bother spinning up the fan. You can still expect reduced lifespan of the motherboard and maybe memory, it all really expects some slight airflow. The good answer to "really fast computer I can't hear" is to put it somewhere else. Long HDMI cable or some variant on thin client and a network cable. An interesting answer is the fanless cases where heat pipes dump heat into the case, but you're probably still under 100W for those. I like a small x64 machine in the wire tray under the desk driving monitors and the real hardware somewhat far away.