Looking to control my fans, having problems - looking for help

Okay, so on my build I'm watercooling and using a 360 and a 240 rad. I want to use 120mm 4-pin PWM fans on the radiators so I can control their speed. However, I want to control their speed using a fan controller, such as the FC5V2 by Lamptron. The problem is, that controllers like these only have 3-pin connectors and therefore don't support PWM - only voltage. That wouldn't be such a problem, EXCEPT, I've bought radiator with low FPI so I can run the fans slow and quiet when needed. I've heard many problems with 3-pin connectors turning the fan off completely if the voltage goes below 50%, which means that I could not run my fans under 50% - completely eliminating the usefulness of my low FPI rads. I would just plug these fans into my MOBO and let it control them automatically, however, there isn't enough connections to hook them all up. HELP. I was looking at an adapter on FrozenCPU that would convert my fans from 4 to 3-pin, but if I can't run the fans slower than 50% I might as well just throw my money away instead of buying those. What can I do?