If you are determined to get the quietest fans that push the highest volumes of air, then you may want to check out the fan reviews on this site.

Noctua makes very quiet fans, but they don't handle any back preasure. They will work as case fans, but the openness of the protective grill may affect the volume of air moved.

The best bang for the buck is probably Yate Loon fans. Get 120mm fans if you can fit them in your case.

Fred

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Blujays1: Spending Fred's money one bottle at a time, no two... Oh crap!