[geoschmo]

If the issue is cost you might help the situation a lot by simply making sure the fan blades and air vents are clean. A thin layer of dust is enough to cause a significant db increase in noise. Also make sure the fan is mounted tightly to the supply and the supply is mounted tightly to the cabniet as vibrations cause noise as well. It won't make the fan silent, but it could drop it below the threshold of what your ears percieve as annoying.