You can also use a program called HWmoniter - Link
that will tell you all your motherboard(and gpu/hdd/ect) temps, the realtime rpm of your fans, and their min/max/current value of each.
I would never recommend slowing your fans RPM without first finding out why its spinning so fast.
The Asus board i have in one of my servers was set at default 100% fan speed when i built it so that's probably why, but don't change it before you make sure their isn't and wont be an issue with heat when changing the fan speed!
P.s. sorry if i repeated anything, i tired to skim the thread to make sure i would not.