I'm suddenly wondering if it's too absurd to imagine adapting a 120mm Paniflo 86CFM $6.95 35dB fan on a normal high performance heatsink (like an Alpha). Forcing the airflow with some kind of "cone shaped duct" (duct tape?...just to be real cheap...)
Based upon my brief encounter with a high output (160 cfm) fan, prior to removing my FOP-32 from service, I'd wager that before you invest big bucks in a big buck HSF, try a bigger fan. Admittedly, no one with a reasonable sense of hearing would want to mount a big cage blower on their PC, but there are high output, smaller footprint fans than that, which can be made to fit the top of your existing HS. Getting the ambient temp inside the case is a close second to a big fan on the HS for reducing CPU fans. You see these horror stories about someone having a 50C CPU temp and then upon further inquiry, you find out that their case temp is 35C. Strive to keep the case temp as close to room air temp. If you live somewhere tropical, strive for an air conditioner
Well I´ve practised this. My very good NoName HSF had a extremely noisy 60mm fan. I removed it and took a 80mm and glued it to the HS with epoxy. Yes it sticks out on the side and top but it´s still pushing more air through the HS than the 60mm ever did. I also reduces the voltage from 12V to 7V (connect between +12 & +5) wich made the fan completely noiseless. Now I´m running my Cely2 600@900 and the CPU temp is 28C at full load (room ambient 25C).
i made an adapter and put a 80mm sunon 42 cfm fan on an alpha 6035 and it didnt do much better than the ys-tech 26 cfm that was on it.i think the alpha is to restrictive cause the fan sounded like it was turning slower than normal.what worked a lot better was to put the 26cfm back on blowing away from the heatsink and mounting the 80mm inbetween the vid card and the 3.5 drive bays and ducting it to the side of the heatsink blowing thru and under the heatsink.my idle temps went from 37C to 33C.
i had the fan hooked to the power supply so i dont know the rpm.the adapter i made put the fan about an inch away from the heatsink and i tryed it in both directions with about the same results.i dont know if moving the fan further away and ducting it would have made a difference