Okay, I see what the problem is now you were trying to address. Sorry, I misunderstood.
The fans you have chosen have a high impedence. Impedence is resistance to starting to turn (sorry, awkward wording. I just can't think of a better way to say it). It's like inertia. It takes a lot of voltage to start them turning but once that resistance is overcome they start to spin faster than you want. This cannot be managed by an analog fan speed controller very well because they still must supply whatever the voltage is that is the threshold to starting the blades to spin. It is just a part of how the fan is made. This is why fans that have PWM ability are so popular. PWM (pulse width modulation) breaks the electrical flow into pulsations but each pulsation has full voltage - enough to get the fan turning. The speed is controlled by controlling how long each pulsation lasts. So PWM overcomes the impedence issue and allows fans to be run at lower, quieter speed levels than analog control does. But PWM is more difficult to fine tune.
Either you need to get some fans with lower impedence or you need to get a custom made PWM controller that can handle higher fan amperage than the PWM built into motherboards can. There's a guy in the classified section of the forum who builds custom PWM controllers. You may also be able to buy after market ready made ones that are beefier. You can also build your own.