I got myself a second hand Corsair HXi 1200w and I just LOVE it.
Last night I noticed the PSU got pretty hot without the fan blowing. I connected the USB cable, installed the software and voila, I was able to change the fan curve.
The software also shows how much power my GPUs are pulling. I love it.
Which software?
There's a USB port on the backof the PSU. Connect it to a USB port and install "Corsair Link". Looks like this:
It's extremely handy to see/know how much power your connected components are drawing. Pretty cool stuff.