The idea that computers must be noisey to be fast is outmoded. When PC's started getting faster they got noisier, so some people began to associate the noise with the speed. But in reality the noise increase has more to do with cheapness than the increased power output. Fans are cheap, and fast fans cost the same as slow fans, but quality heatsinks and design are expensive (relatively).
Now that there is an established backlash against pc noise the market is full of options. You don't even have to be a modder anymore. With just a bit of research and knowledge you can fill a Newegg shopping cart with all the parts needed to make a fast, powerful, but quiet machine. And it won't cost significantly more than a loud but equally fast machine would.
As for the semantics of "silent": all that really matters is the relationship between the PC's noise and the ambient noise of its relationship. A 50dBa PC is "silent" if it lives in a machine shop. The same pc would be a screamer in your bedroom. There a 20dBa machine would be "silent". Pursuing anything less than ambient is an academic challenge only. Not that that makes it a bad thing, but it just puts it in the category with OC'ing-as-a-hobby. Most of our articles we post at SPCR fall into the first category, while our forums tend to be of the "academic" variety.
