My S9 is not more noisy than an S3 at the moment. Plus heat output is great as it saves on heating at this time of year.
You're saying the S9 is about the same noise level as an S3?? Or your under-clocked S9 is similar to S3?
no underclock needed. In lower temp environment autotuned 11th S9 may have fan speeds of 3.8K and 2.2K rpm. That's S3 numbers or even lower.