Dave,

Youdaman. I can appreciate your admitted nutty-ness :)

The thought of noise-cancellation crossed my mind as well, only in the form of an external unit that you may find in such places as The Sharper Image etc.
But frankly, I do not have a whole lot of confidence in the effectiveness of these gizmos.

But if you are THAT serious about it, perhaps you should consider immersing all heat generating components in non-conductive oil. Saw some guys at the amdmb.com forums talk about that. It would eliminate ANY need for fans. It would also get terribly messy if you like to swap components a lot. :-)

I'm hoping the next iteration of the Koolance case (apparently due in August) will handle higher CPU temps at low fan RPMs.