ASUS P8Z77-V LX PWR_Fan Control

I have built a computer (like many here :D) and I want to control one of my fans connected to a PWR_Fan header.

I have the asus p8z77-v lx motherboard, it has the cpu fan header, two channel fan headers and 1 power header. I have 3 chassis fans, the power fan is currently running at full RPM and I want to lower this. The fan is not in a critical position so I just want to limit it to say 1000RPM rather than the current 1600RPM.

I have installed ASUS AI suite which includes the Fan Xpert+, but not Fan Xpert2 because I beleive is not compatable with my budget motherboard. I have tried using that and the BIOS with no success. :( It is worth noting I am not an expert at using the BIOS I may have missed the appropiate setting.

Any ideas how to limit the power fan's RPM?? All help is appreciated.

I don't think Asus will let you change the speeds of the fans connected to either of the CPU fan headers unless they are PWM. I have a similar board and I found this out through some fan testing.