The ultimate goal of any fan is to cool your system with the least noise. Temperature, however, depends entirely on your specific system; its case, components, ambient conditions, internal airflow, etc. There is zero way to predict this reliably ahead of time. It may very well be that your system doesn't need a lot of CFM to keep cool enough. Or maybe you have a 3770K OC'd to 5.2 GHz in a stuffy room with no A/C down in Alabama sharing space with a bunch of vid cards in SLI/Crossfire, and you need massive CFM.
In a relative sense, temperature will be related to airflow through your heatsink or radiator
. This unfortunately is not just a matter of a fan's nominal CFM, but also its static pressure and the characteristics of your rad. Why am I spelling this out so explicitly, when I'm sure you understand these points already? Because, well, you've already answered your own question in a way. Nobody can tell you exactly what will work for your system. You have to make an educated guess based on various objective and subjective reviews, prevailing wisdom, and knowledge of your own setup. Or else you have to pay the piper and experiment yourself with a selection of fans.
Just keep in mind the above, and realize that it means the following points of comparison are arranged in decreasing usefulness:
- Your own subjective noise perception vs objective temps on your own computer for a selection of fans.
- Your own objective noise measurement vs objective temps on your own computer for a selection of fans.
- Someone else's objective noise measurements vs objective temps on an identical computer for a selection of fans.
- Someone else's objective noise measurements vs objective airflow through an identical or similar radiator for a selection of fans.
- Someone else's objective noise measurements vs objective airflow in open air for a selection of fans.
- Someone else's objective noise measurements vs objective RPM in open air for a selection of fans.
- Manufacturer's claimed noise measurements vs airflow for a given fan.
- Manufacturer's claimed noise measurements vs RPM for a given fan.
- Someone else's subjective noise assessment vs any variable for anything (unless in conjunction with above data).
- Your dog or cat's reaction to your speaking the name of a given fan.
- Anything said by YouTube commenters.
Since points 1, 2, and 3 are usually not available, unless you have already bought some fans and tried them yourself, that leaves points 4 and 5 as usable research, with 9 being useful if and only if it is used to corroborate or detail that data. Points 6 and below are not useful on their own.
So what fan reviews would I trust?
SPCR's, for one. Both the objective official reviews as well as the prevailing opinions.
Some of the xbitlabs tests are well done.http://martinsliquidlab.org/category/fans/
has excellent tests for fans on rads, with sound-normalized youtube vids to demonstrate so you yourself can hear the noise characteristics.
There are probably some more out there, but you have to do your own research and make your own conclusions.
FWIW, I recommend the Scythe Gentle Typhoons (AP-15 or AP-14), as they give ultimate CFM vs noise through a rad, but they are also known to produce a bit of a hum at higher RPMs.