Quick update for the ones who are still working on fan noise: the RDS does come with high quality Nidec fans, no problem there, but they definitely have a “beehive” ring to them once they spool up—sure, all fans do, but the Nidecs are really whiny at medium to high speed. Though my previous attempts with all 9Pxx/9Gxx Sanyo Denkis failed, as they refused to “listen” to the PWM signal applied by the router, I managed to find a good replacement: 109P0412P3H013. It does not come with vanes like the Nidecs do, so the flow is not as directional, and their max speed is about 9k RPMs as opposed to 18k for the Nidecs, but they make a difference in noise at similar RPM, with a frequency profile noticeably lower than the Nidecs (high freqs are much more noticeable then lower freqs). And yes, they will accept the RPM signal from the router, and the top speed of 9k RPM is plenty based on what we’ve seen so far. I also tested them in a CCR2004 (the r2 flavor w/ PWM), and was equally successful. They seem to be much more lenient when it comes to the PWM signal they will accept. Note that the batch of fans I used dates back to 2019, I can’t guarantee newer batches will behave the same.
Long story short, if you don’t care about noise, stick to the original Nidecs, they’re great, but if you do, do me a favor and skip the Noctua nonsense and try the Sanyo Denkis, they work and are much better fans overall.