Replaced the Thermalright 140mm case fan with a Noctua NF-A15 PWM fan. Ohh my the Noctua fan is quiet.
There was a problem with the Thermalright case fan, it wouldn't spin smoothly unless the BIOS PWM multiplier was enabled, and there is a bug in the Gigabyte BIOS where it doesn't enable the multiplier until after the first reboot after a cold boot. The Noctua runs fine with the default fan speed setting.
It comes with rubber mounts, and they popped right into my bracket, and further isolate the fan from the rest of the chassis. Not that it matters... the fan has no vibration at all.
The Thermalright CPU cooler fan has always been silent, so I have no interest in replacing it.