http://www.nexfan.com/80mmfans.html
Take your pick CVW.
I ordered two of these and am very pleased:
http://www.nexfan.com/evcafan80bab.html
You can get the three pin or Molex connector.
Noise-wise fans with a dBa, decibel, level between 20 & 25 will be quiet. It follows, the higher the dBa level the noisier the fan and usually moves more air. One fan with a dBa level of 50 will be noiser than two with a 25 dBa level. Don't ask me why, das' jest de' way it is. 30 CFM is sufficent for most cases because I figure a mid tower case contains 3 cubic feet of air and a 30 CFM fan will theoretically "change the air" in your case ten times a minute. Don't forget, the PS, power supply, fan also removes hot air from the case.
Your post provided sparse info to work with, but here goes.
First, an Old Indian computer trick:
Back before they had temp monitoring software utilities we'd take a mercury thermometer, like your Dr. uses, and stick it between the PS wires in the TOP of the case, close the case, let it sit a couple hours then take a reading. (Don't allow the mercury bulb to touch anything.) Do what ever case mod, like add a case fan, put the thermometer back EXACTLY where it was before, close the case, leave it there a couple hours then take another reading. Don't forget the ambient temp directly effects the readings. Crude but effective means of seeing what your temps are doing as you make the case mods. I suggest doing one mod at the time then see how the temps read. Go slow, be methodical, write it down, do it right. In so doing you remove all guess work and have relativey accurate data to work with because you KNOW what effect the mods have.
TIP: Go to the pool dept of a store and buy an encased mercury thermometer, not nearly as apt to break and you can secure it in place with a twist tie.
Case cooling covers a wide range of variables and I tried to give you a basic place to start.
One last comment: If you put two 30CFM fans in and your case vent is not large enough you might "starve" the fans and and it may be prudent to use an intake fan. Most cases have holes in place to install an intake fan over the front vent. Again, don't forget to figure in the PS fan.
"i have the lian-li 60 B and it has a top blowout fan a rear blowout fan and two front intake fans."
Sounds like a real nice case with great cooling options.
If it were me I'd first install one top exaust fan, then take the temp readings. Next I'd go with one intake fan and take another reading. All kinds of ways you can skin this cooling Cat, so have it, enjoy your computer and LEARN. If you have more questions come on back and we'll be glad to help if we can. OldBird
PS Neat monitoring utility here:
http://www.podien.onlinehome.de/CPUCOOL.HTM
Another here, scroll way down to the bottom of the page:
http://www.almico.com/speedfan.php