Get a fan controller and 2 panaflo L1A fans. The sonata is only built to have 2 120mm fans in it. And with the thickness of those fans you will need to be sure to put the mother board in first as you won't be able to put it in after putting the fans in.
I cannot here my sonata right now with 2 L1A's in there and my vantec fan controller has them on the minimum.
Generally the biggest sources of noise are the video card cooler, cpu cooler and power supply (1,2 or a combination of all 3).