Cooling the brave new world

Well, no offence taken by me!

FWIW, I've been doing some saving as my current PC is getting somewhat
long in the tooth (i.e. it's over three months old), and I'm looking
to build something top-end now that's going to last me two or three
years as my principal PC.

I'll retire the current one to my PC boneyard where it can sit with my
windows 98 box and they can both talk to each other about the good old
days.

Nonetheless, I am still after as silent a solution as possible - my
two existing PCs are both passively cooled, and I've grown to
appreciate the silence. I'm not averse to "some" noise, but the less
the better... so, any useful tips or pointers would be much
appreciated.

Of course, if there aren't any, banter and mud-slinging would do )