hello, haven't been on this forum for perhaps a decade and god, hadn't it been very useful in the past!

I am having the following PC, not the freshest on the bloc, but it is still serving me well right. I do mostly office stuff, web, photo editing, every other moon some non-intensive gaming. It will also serve me as a Plex server in the near future.

i5 4690T (TDP 35W) cooled by a Scythe Big Shuriken 2 Rev. B and a Noctua 120mm
Asus H97I Plus (integrated graphic)
2x 8GB Crucial Ballistix Tactical LP DDR3 1600
Samsung nVME 970 1TB (monted on a nVME PCIe adapter)
2x WD Red 2TB (soon to be replaced by 1 WD 8TB)
connected via LAN cable, but perhaps getting in the future a M2 WiFi module
all hosted in a NCase M1

The PSU is a be quiet! SFX POWER 2 300W, which is still performing very well to my untrained eyes, so no real reason to give it away.
However, it is indeed quiet when compared to the PSU I was running on my P4 of 10 years ago, but really I find it quite distracting, as it sits right next to my ears.
I am basically trying to find a completely/extremely silent PSU that is not overpowered and that is modular too. It seems a hard equation to solve, maybe I should start my own business producing my own SFX (I have space for a SFX-L in my case, just need to find a way to mount it), low-requirement, fanless and modular PSUs!
If I refer to PC Part Picker, it estimates my (maximum) draw to be 149W.

I am intrigued by:
. Silversone NJ450-SXL: fanless (!!), modular (!!), but able to provide a beefy 450W. On the efficiency/power draw ratio chart the lowest load plotted is 20%, coming with an efficiency of 90%, who knows what happens below that? That 20% means a load of 80W; my config I think @ idle/low load is approx. 30/40W.
. Silverstone ST30SF: fanless until 55C is reached (!), not modular, provides a more ideal 300W (!)
. Corsair SF450: zero-RPM mode - unclear at what temperature the fan kicks in - (!), modular (!!), again giving out 450W as the SS NJ450 - the latter would then be an obvious pick.

I am not adverse to a PicoPSU, I have used them in the past for a low-power torrent server, but I would need to find a silent (i.e. no buzzing or other funny noises) power bricks to couple it with and to embed said power brick in the PC case.
Or I should perhaps bypass the fan and connect it through a fan controller, so I can spin it at say 20%?

What would you all do?
Thanks

I would recommend to check HDPLEX 200W NANO ATX COMBO, its a like PicoPSU but its a little better with the power brick meant to be installed inside the case. But crosshcheck it would fit your NCase M1.

I'd be surprised if your system ever exceeded 80W.

A PSU which you might consider is the Seasonic Focus SGX 450. From my local supplier it is about the same price as the Corsair 450w.

According to this review of the 500w model the fan should not turn on below 150w system power draw. With the 450w this point should be around 135w, which with your existing hardware means that the fan is not likely to turn on at all.

Indeed I doubt I ever exceed something like 80 or 70W.

I have actually been dreaming about the HDPlex since it has been linked, really nifty piece of kit, it looks like a much better improved PicoPSU.
Main problem I have with that is, the odd shape of the DC-AC. I have been in touch with Larry already, I think the AC-DC needs to go length-wise and I only have as much clearance as the SFX standard (125mm).

The SeaSonic looks very, very interesting.
I love indeed how it has guaranteed silent operations under 30% load, and I love even more than in the end it has a fan, so if things get hot, the fan will spin up.
When back in the days I was running that torrent server, I always had the (perhaps unjustified) fear that things would go awry due to the PSU potentially over-heating.

I also love how with the SeaSonic there are provided so many different lengths SATA cables and a 10 year warranty!
And it is cheaper than the HDplex counterpart and it has a more "standard" shape.
but TH shows it has only 73% efficiency under a load of 26W
You can never win!

Well if your goal is low power efficiency and you want to go as low as you can, i would give a shot to a picoPSU-90 + 100W Adapter Power Kit, the brick is small, its very likely you should be able to shove it inside the N1, just make a PSU cover plate with the power connector or something alike.

I have the SF450 platinum and a low power system (see signature)... I've never heard the fan turn on, even in the summer with 95F ambients. I just don't pull enough power to trigger it. I think they claim the fan turns on based on wattage, not temperature, but am not sure. In any case, I've never pulled over 90W (stress testing, it's' usually much less than that, it idles at 30W per a Kill-a-watt), and have never heard the fan. I recommend it.