Modifying motherboards is not for everyone - but certainly an option.
verndewd - I would suggest you reconsider your position about fan noise, however. I worked air traffic control radio maintenance in the Air Force for many years and all our transmitters had fans for the lighthouse tubes. Individually, each fan was not too loud, but with a room full of radios, it was certainly audiable, but never really bothersome.
However, long term exposure to the same drone causes permanent hearing loss at some frequencies. Not cool - as it now affects my hearing.
Additionally, many folks have more than one computer in their work or home office - with just 2 PCs, 10 - 15 fans is certainly noticable.
Also, more and more folks are using their PCs to watch DVD movies, or they integrate their PC into their entertainment centers. No one wants to hear a bunch of fans whirling about during quiet passages.
Also - though not a hard set rule, quiet fans are typically made to tighter tolerances - their bearings are more precise, resulting in less friction and less noise from the fan motor - meaning, they are better fans and are likely to last longer. Of course, if the fan is simply made to blast huge amounts of air, then "wind" noise is a given.
IMO, the goal should be cool AND quiet - not one OR the other.