Not really a “power” PC, but I had a little play with my XPS which I bought during lockdown/graphics card hell as a cheap way to get a 3060ti.
The cooling was an absolute joke. Single 80mm exhaust fan, hard drive blocking most of the airflow from the front of the case even though there was a free bay at the top of the case which wouldn’t cover the vent grills.
Moved the HDD and bracket, put as many Noctua fans as would fit in the case, added a VRM heatsink and swapped out the stock intel cooler for a tower cooler.
GPU temps unchanged, but fans max out at 70% not 100% which is a massive difference in noise. CPU temps down 20C (!!!) and the PC runs so much quieter.
The hard drive at the right was where the fan at the bottom of the pic is, completely blocking any airflow. Genius.
Oh, and the memory wasn’t running at it’s maximum rated speed either. FFS dell!