I'm made some purchases to quiet my new PC as well, (tracking them as we speak) and should have everything by next week). I've got a Tiger MPX dual CPU motherboard with 2 AMD XP1700+ with the retail fans. It's a pretty loud machine (about 75db at the back of the case, and about 50db at 2 feet).
My hopes are to reduce the noise to a almost dead silence, but that remains to been seen (heard). I'll post my success or failure next week when I get everything installed.