Hey Buddzy,
Noctua NF-P12 120mm
These babies may not be the absolute cheapest, but they are the absolute BEST that will last you as long as you need them. They pull about 54-55 cfm @ 1300rpm and are the QUIETEST fans you can get on the market today. Given the legal standing of our interests here on RIU, noise is surely a concern.
The price ranges from $15-$19 CAD @ many online retailers.
Check out a review:
http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/3792-noctua-nf-p12-120mm-fan-review.html
I just put two of these on my Prolimatech Megahalems Heatsink to cool my OCed 920 i7 and they're great
Also check out CoolerMaster Excalibur. It has a higher CFM of 85.6 @ 2000rpm which may be a better option for you.
MASSCOOL FD12025B1M3/4 120 x 120 x 25mm Case Fan - 96 cfm
Silverstone SST-FMC3XW - 103.5 cfm @ 3000rpm
I don't know, I could go on and on, but check out newgg.com, tigerdirect.com etc. You'll find one
GL!
Check this out for sure:
http://www.newegg.com/product/product.aspx?Item=N82E16811999344 114cfm @ 2400rpm <---
Delta TFB1212GHE 120x38mm Extreme High Speed - 220.01cfm @ 4600rpm... if you want to go hardcore, don't think its too expensive.. 27 USD @ http://www.sidewindercomputers.com/de12tfexhisp.html
check all these Delta's at NCIX.com. They seem to be the highest cfm : http://www.ncix.com/search/?categoryid=0&q=delta