The percentages refer to the fan PWM duty cycle, so it depends on the fans not the particular graphics chip. So figures of 10% or 30% duty cycle do not mean much without knowing what rpm the fans run at at that setting. It would help if reviewers who commonly show GPU-Z screen shots would include some of the Sensors tab at idle and load. I have found one reviewer who has done this for the Asus GTX 660 Ti Direct CU II. At idle this shows the fans set at 10% duty cycle as expected. This results in a fan speed of 1080 rpm. What did 30% duty cycle on the Phantom GTX 560ti translate into, around 1150 rpm? As I understand it, the Direct CU II fans are 70mm and the Phantom had 80mm fans. So although the Direct CU II fans are running at idle at a similar speed to the Phantom they should be an increment quieter.
Thanks! Yeah, I believe it was around 1200 rpm @ 30%. I'm currently looking into getting the MSI Twin Frozr GTX 660, which seems to be one of the most quiet 660 cards along with the Asus (which unfortunately is quite a bit more expensive here at the moment).