Always relevant: http://www.tomshardware.com/reviews/geforce-gtx-670-test-review,3217-14.html
It's a bit old and doesn't include all the brands out there today + some of them have had their coolers tweaked or changed, but it'll give you some general idea on the noise levels.
The most noise efficient cooler is the Asus DCUII, which comes in both 2- and 3-slot versions based on the card. I believe the standard 2Gb 680 models are 3-slot and everything else 2-slot, including 680 4Gb version.
That said, I have no idea how well the 2-slot 4Gb version of 680 fares. There just aren't any reviews online I can find, but we can safely assume that it probably doesn't perform as well as its bigger brother.