
Fractal
http://www.overclockers.co.uk/showproduct.php?prodid=FG-001-FD&groupid=701&catid=57&subcat=4
Properly silent at 15db unlike most of the other "silent" ones being 20db but still puch 38CFM. They are expensive though, but from when I spent ages researching the best combination of price, CFM and noise level I chose those ones. While there are quiter (12db) fans, they tend to move only half the air etc, and cost a few quid more per fan.
Akasa ones are not Silent, Yateloons are quiet if you under volt them but then they dont puch as much then etc.
Get some of the rubber mounting pins as well, they will help a lot with vibration if your going for a totally silent build. Although they can be had cheaper by looking for people selling them on who buy them in massive bulk from abroad.
so many threads on this subject.
http://forums.overclockers.co.uk/showthread.php?t=18209662
http://forums.overclockers.co.uk/showthread.php?t=18187968
http://forums.overclockers.co.uk/showthread.php?t=18181093
http://forums.overclockers.co.uk/showthread.php?t=18177724
http://forums.overclockers.co.uk/showthread.php?t=18167810

What about these ?
Xigmatek 120mm Crystal Red LED Fan
- Dimension: 120(W) x 120(H) x 25(D) mm
- Voltage Rating: 12 V
- Starting Voltage: 7V
- Speed: 1500 R.P.M 00 R.P.M.
- Bearing Type: Long-life bearing
- Air Flow: 68.33 CFM
- Life Expectance: 50,000 hrs
- Noise Level: <20 dBA
best combination of CFM and noise I have found so far.
is this accurate ?
Is that the XIGMATEK XLF-F1253?
Got 3 of these in my air cooled case and they sure do shift some air.
Controlled by a fan controller, Scythe something or other.
At 50-60% (about 1000rpm) their pretty quiet. When at full whack they get noisy, not the front or rear ones too much but the side fan is. That I never then to increase over about 40% ish.
Few pics in my sig link.