I promised to show a picture, so here it is:
http://www.scythe-usa.com/
http://www.enermaxusa.com/
It's absolutely incredibly quiet.
It has lowered the noise-floor considerably, meaning I can enjoy my ultra-fi audio-setup that much more.
The large fan (12cm) runs at ~1160 rpm, compared to the previous 8cm fan which ran at 2500+ rpm.
There are ways of making the fan run even slower, which would make it inaudible completely, leaving mostly the hard-disk as noise-source. So ya, I'm lovin' it.
Oh, and just a 'little' footnote: I almost broke 3 essential parts of my computer (

).
First I was taking out the old CPU heatsink/fan. It seemed stuck so I pulled on it and it came out (it wasn't attached in any way). Well, the cpu had come off TOGETHER with heatsink. They were 'glued' together. Then..
I was taking out the old PSU and I let it drop inside the case and it fell down against my (brand new) videocard, and also bended a couple capacitor on my mainboard. There was a clear scratch on the videocard and I was worried it had chipped some of the copper. The two capacitors on my mainboard were *really* bended. I left them alone and prayed.
Then came the moment I had to put the cpu back in, which was still stuck on the heatsink so I looked at it more carefully. Damn, it was really stuck. Finally I used a screwdriver to whip it out with turning momentum. It worked. It came off and fell on the wooden floor, and I thought, oh ****. Picked it up and censored, it had 5 pins bent. So it took me 5 minutes to carefully bend them back, which seemed to work. Had to push it in on the mainboard socket pretty firmly to get it in. Another thing that could have been broken by now..
Finally all was installed and I turned it on and windows came on. What a miracle.. I run good..
Oh, and with this heatsink you can position the fan on all sides, and along the widest side is the best, except then it would blow against my videocard (which also has a fan that's usually silent, but you don't want it having extra heat). So now it's blowing the heat more outside.
This is an AMD system btw (Athlon 64 X2 5000+, 2GB, etc).