My stock fan ran about 4200 RPM. Using a Zalman Fanmate, I had lowered the RPMs to about 3700 (as measured by Motherboard Monitor) to reduce the noise. Unfortunately, reducing the fan RPM increased my CPU temps by 2C (46 max), but the noise reduction was worth it. As far as a noise comparison, I could readily hear some whining from the stock CPU fan somewhat in a quiet room, but I can barely hear the TMD fan at all unless I put my ear right next to the side of the case. The only sound I hear most of the time now is the faint sound of air as it enters and leaves the case through the intake and exhaust fans.
The real reason for replacing the stock Evercool fan was that I had a fan bearing go bad after only a month or so, causing the stock fan to rattle occasionally (very annoying). This was on my SECOND Evercool fan - the first fan had a bearing go out at about 3 days, and the fan was replaced under warranty by the vendor. I decided not to try another stock fan, but to try the TMD instead.
When you consider I only paid $17.99 for the EC CUD-725 (nexfan.com) , and $10.99 for the TMD fan (phamcomputer.com), I got a whisper quiet, yet great performing heatsink solution for a lot less money than most folks are paying for comparable performing AX7 and SLK-800 fan combos. It just goes to show that price is not always the determing factor in good heatsink performance.