If you need fans that push air well and with acceptable noise and longevity, try these:
http://www.newegg.com/Product/...x?Item=N82E16835185006
When you buy two the price drops to $14 per fan, $35 shipped for both, and they are rated at 63CFM at 28dBA.
EDIT: Re-reading BonzaiDuck's thread (and his post on mine) I think you could benefit the most from his method. Ducting will focus the airflow over the components you need to cool while getting the most out of any powerful exhaust fans you install, eliminating the need for installation of extra cooling fans over specific components.
I would still consider replacing the stock CPU HSF, but make sure it fits a ducting plan should you decide to use the method.