http://www.amazon.com/gp/product/B00A460TK6/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
will result in near silence . One fan needs a slight mod to the edge of it.
I have two from my s-5 sitting in a box.
they work okay on the s-5 due to the open case design ,but they work great on the s-3.
Would they work with the S1? The S1s I bought don't have stock fans with PWM they are hard wired in and always run at full clip. I wanted to change the fans out but no point in investing $ on an S1. I can put them in my room with an open window (good old Canadian winters) and keep the internal temp at 25C but can't sleep with the fan running 100%. It wouldn't be a bad investment if I'm going to use them on something else later
I'd be willing to buy them off you if they have PWM.