There aren't many choices for quiet and LED with fans, not sure why. I haven't found many choices.
I personally have 10 of these:
<A HREF="http://www.coolerguys.com/840556014034.html" target="_new">http://www.coolerguys.com/840556014034.html</A>
If you cut off the thermal sensor they will run at low speed all the time, which happens to only be 19 dba. I tried both ways, with the thermal sensor cut off they run whisper quiet, with the wires spliced back together, they run at full speed all the time, which is very loud, but I don't mind.
That is the only LED fan that I know of that is less than 20 dba.
If you are willing to go up to 30 dba or less, there are many fans in this range, and you can get much better LED fans (better, meaning they glow more). Many manufacturers still consider under 30 dba, a "quiet version".
If you search, you will find most LED fans are under this 30 dba figure.
Guess it just depends on how quiet you want.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>
Overclocking Results: <A HREF="http://Mr5oh.tripod.com/pc2.html" target="_new">http://Mr5oh.tripod.com/pc2.html</A>