I just replaced the power supply in my machine with a nice seven hundred watt, Antec unit and the three case fans as well are now Antec.
I really wish I had taken a decibel reading before to have some tested documentary numbers, but my trained ear is telling me that this friggin box is at least six decibels quieter than it was before.
One fan failed a couple of months ago and the generic jobbie that I put in, to survive the emergency, was quieter than the one that was dying, but these are very much an improvement and I did all of them at once this time. A bottle of comressed air didn't hurt anything, either.