I selected this case for a DAW build because of it's size and the sound dampening material. My build has three 120mm fans in it and I can still hear them if I really try. By comparison, a gaming computer with 3 similar sized fans is 5-6 times as loud.

There are rolled holes for wire pass throughs where I needed them and a bunch of them that I didn't need at all.

The only think I didn't like is having to remove the power supply to use two of the HDD mounts, so I didn't use them. I managed to get a spinner and a SSD in the lower cage and a hot swap tray in the DVD rack. (Who uses DVD drives?)

Bottom line: if you're looking for a smaller case with less noise this is the one.

I originally built my system early last year right before the pandemic shut everything down. I was trying to go for a sleeper build by using the case from my old Compaq Presario SR5450f but airflow was very limited so everything ran hot and the fans got loud. I did some research and found the Cooler Master Silencio S400 to be what I was looking for.
In the pictures, it shows up as a lighter grey but in person, it is a dark grey almost black which I found I liked better. It has a stealthy vibe to it and I like that there's no RGB lighting all over the outside of it. The materials are very good and solid throughout for the price. The side panels are heavy and stiff feeling to where when you knock on them, it sounds like you're knocking on a solid piece of wood with a rock. Some online reviewers and Youtubers noted that temps were higher with this case but honestly, it's not that bad at all and if you feel you need more airflow then you can just swing open the front door of the thing allowing your fans to pull in more air. The dust filters seem to be doing a great job keeping stuff out. The pictures I posted with this review are after about 3 months of not cleaning it. I keep my computer on the floor too so it can pull in cooler air and not take up desk space but it hasn't affected dust build-up at all. I was able to fit two Noctua NH-A14 fans in the front as intake as well as two on the top as exhaust and an NH-A12x15 (since there was no Chromax version of the NH-A12) in the back as exhaust. My fan setup could be contributing to the lack of dust with air pressures and all but I have never experimented with that. I wish the case came with both the tempered glass panel and the steel one so you'd have options since the model with the tempered glass panel is harder to find. All in all, I'm very pleased with this case and I plan to use it for a long time. I'd highly recommend this case if you want something quiet, stealthy, with no RGB or any gimmicky features.

Although outdated by some standards... here are the specs:

AMD Ryzen 5 3600
Gigabyte Aorus B450M
Noctua NH-U12s Chromax
Noctua NH-A14, NH-A12x15 Chromax
Gigabyte GTX 1660 Super (I wish I would've bought an RTX 20 series instead of waiting...)
16GB G.Skill Ripjaws V Series 3600MHz
Western Digital SN750 1TB SSD
Seagate Baracuda 2TB hard drive (the loudest thing in the system)
EVGA 550 B5 PSU
And of course the Cooler Master Silencio S400

The overall case structure is wonderful all the cables line up perfectly with my Asrock X570M Pro4. I have 2 Noctua NF-F12 iPPC-24V-3000 RPM fans one on the rear and another mounted on the top. My NZXT Kraken x63 is mounted on the front of my case ( it is 280 mm rad very thick with my 2 Noctua NF-A14 iPPC-3000 PWM fan mounted outside the case which can produce quite a bit of sound if I do not have them turned down.) The front panel will fit but it must be forced on due to the size of the fans. In hindsight, I should have gotten a 240 mm rad instead of the 280 mm rad but the 3700x CPU draws quite a bit of power when oc'd so the extra cooling is nice. My MSI Gaming X 2070 Super was much larger than I anticipated therefore when building my next PC I will put more consideration into spacing. Finally, with the 4 SSD bays and 4 HHD bays, the system is ready for any setup one may desire. In actuality, one could install 2 HHD's in the front of the case without issue instead of the SSD if the mounting screws are utilized.

The Cooler Master Silencio S400 is a top quality case, not even for the price, but overall. I used this case in a build for a friend and now I want one! I might get the S600 for myself though, so I have more room to work and put my stuff.

Pros (plus many more):
1. Filters for air intake (big one up front, one on the bottom for the power supply, optional one one the top (included)
2. Quiet with the padded sides and a weighted reversible front door that closes magnetically with a satisfying clunk
3. Good airflow due to many fan placement options and cable management options around the back
4. Subdued look with no flashy advertisements or gawdy colors
5. Very easy to install 5.25" drive from the front, and 3.5" drives on the right side

Cons (nothing worth taking a star from the overall rating):
1. 3.5" installation on the left side, under the 5.25" drive is easy... until you try to connect and route the cables that should be plugged in on the back of the drive
2. Side panel screws should have a few more pennies spent on them, never get all of them on right the first try
3. Feet of the case should be a little taller so the case doesn't have to be on a hard surface to get air into the bottom fed power supply

K. So, it's perfect in all respects minus the following:

The normal side of the UPS/HDD shroud needs to open or something. GL flipping the internal ECO switch on a UPS without that. Or other stuff you may have tucked under there.

You may be able to fit 140s in the front, but you're not gonna get any more airflow because while you have the mount holes, the opening is the same size. Myyyybe a slight bit difference, but... just consider those 120s unless you already have 140s.

The screen cover for the top really needs to work together with the solid cover. It's one or the other. Now mine's blowing out so I just put the screen aside, but I'd like to be able to have that magnet screen and still have the top cover.

The bottom screen is clearly an afterthought. It's just a loose screen. Kind of a joke, but better than nothing I suppose.

Finally, "Silent" case is a unicorn. I didn't know, I wanted to believe, I know better now.

All that said, this case is gorgeous to look at. The cable management is good. Lots of drive mountings, with expandable front port - rare these days, especially in a micro tower. It was fine to work in considering the tight space of the form factor. I didn't get left thinking "who designed it this way and why would they do that" at any point as far as mounting and cabling.

I did have some trouble with the HDD cage having the extra brackets for a 3rd HDD. Kinda tough to remove if your cables drape below the shroud at all, because it catches. And with a 3rd drive it would be tough. I thought the extra option of a 3rd would be nice for possible random need to expand, but realistically it's too tight. But, some tin snips could take care of that, though i managed without any such modifications and it's not a design problem, just a byproduct.

Great case. Built well, sturdy, pleasant to look at, and one of the few ones of this caliber without clear sides and with expansion on the front and nearly every option you could want. And, there arent any sharp corners or anything but you should still take off your smartwatch ;)