Whatever, I have 3 seasonic 380w psu's on systems with mid-range gpu's and they are all stable even overclocked.. and quiet indeed. what has been recommended so far is pretty good.. i'll throw a few more into the mix for fun
scythe ninja (a lot of other scythe hsfs)
thermalright anything with a quiet fan
zalman 9500 downthrottled
zalman aclu's downthrottled
thermaltake (GASP) big typhoon (doesn't sound like a typhoon)
65w amd 3800+
any intel c2d (i dislike intel but i can't lie)
amd semprons
avoid any intel netburst AKA p4
many vidcards come with either:
silentpipe (i/e gigabyte)
or nvsilencers (although possibly rebranded, these are easy to spot. the stock cooler is usually a small lotsa finned black fan. the nvsilencers or 'clones' thereof use larger (fewer) finned fans)
you'll be hardstruck to find decent performance AND low noise from anything other than the above in games
antec p150
antec p180
silverstone temjin (tj06, tj07.. etc)
lian li's being aluminum are usually not a good choice unless you are big on LANS.. aluminum cases are harder to silence and have more resonance in general
larger >120mm > 80mm > anything else for case fans, cpu fans, psu fans, etc
powersupplies:
anything seasonic
lots of fortron
most enermax
some antec
a few others (most are rebrands of another company i/e ocz, corsair, thermaltake, etc especially)
motherboards with passive heatsinks (you'd be suprised how high of a percentage of people's system's loudest component is the motherboard northbridge chipset fan (often 40-60mm and SCREAMERS) this is not ALWAYS true though, there are SOME (very few indeed) small fans that aren't loud (but generally smaller fans have to spin faster and have higher frequencies which are more annoying. however don't make this the sole factor, MOST mb chipset fans can be replaced (I'd say 95% of them) with quieter fans or hs's
hard drives: samsung > western digital > seagate > hitachi > maxtor (this is an extreme generalization, although actually QUITE true in reality!!) do some research on silentpcreview.com to find out more
(suspending drives like bob said with elastic improves VIBRATION noise quite a large bit.)
did I leave anything out?? I'm a few beers deep. excuse grammar/rambling. this is too much fun for geeks like me.
-kenji