My personal recommendation is 2x S3 fans if you've got them lying around or my go to is the SP120 Performance editions
/994pId][Without affiliate] /aTtqhF][With affiliate]. There are also PWM versions if you think you'll need it in the future
/464xEn][Without affiliate] /ULI5ny][With affiliate]. They're right at the barrier between high performance and not being too annoying and I generally use them on most miners I silence.
Fans like the SP120 will plug directly into an S5 and aren't silent but aren't horrific. They're ~2200 rpm with a high static pressure which is required in a situation like this more than just straight 'CFM' ratings. You don't tend to get LEDs on fans like this and above as they usually all go into servers and such like. There is a similar AF120 series which is LED, but isn't suitable for S5s as they're not powerful enough.
If I may ask a follow up question. How would the Scythe Grand Flex PWM compare to the SP120's? On paper they spin up to the same RPM, similar dBA, but the CFM and Static pressure is much higher on the Grand Flex model. Has anyone tried this on the S5?
I'm still waiting for my s5, but I am trying to get my research done now because noise will be an issue. I have 8 of the Grand Flex fans in the box and it would be nice knowing I don't have to purchase new fans. My goal will be to get the S5 as close to S3 noise levels as possible without sacrificing much cooling.