Build quality is very good, the thing's sturdy and the metal sheets are very thick. Has holes in the right places and plenty of spacing on the back side for clean cable management.
As for noise reduction, worse than I expected, but that's probably because I expected too much. Every comapny advertised "silent" so I actually expected that :/. Instead what I found was that noise reduction simply reduces noise, it doesn't eliminate noise, so you can still hear whatever you can hear. Hard to explain how quiet something is in words, but you can definitely hear it. If you live in a quiet environment like I do, I don't even think it's possible to make a "silent" PC.
My setup also suffers from 2 other factors:
1. I have the box set up on top of the desk, so it's rather close to my head. If you have it under the desk it would be more quiet.
2. A lot of my other parts aren't really designed for quiet operation. Like my PSU is just a standard one because I didn't want to fudge out loads of money for a completely fanless or dual mode (fanless on low power usage) PSU. And my graphics card is pretty standard with 2 small fans, which probably run on high RPMs. Don't even think it's possible to get a powerful yet quiet graphics card unless you are willing to rip off all the cooling compents and replace it with liquid cooling.
3. I took the one with a window. That window is plastic, with no noise reducing foam on it, and the window side is the side facing my head. The windowless version would probably perform better.
To be honest, I chose this box 70% because of looks, and only 30% because of quiet. That's also why I got the window version, knowing it would be worse at keeping noise in.
EDIT: I tried to listen to where most of the noise came from. Seems to be PSU, that fan is right at the back of the box and there's no foam or whatever to stop noise.
ZiNgA BuRgA Wrote: [ -> ]Dust filters could be a nice thing to have, but I can't quite easily see which ones have them :/ Does the R4 have them?
It has dust filters on the positions that are intended for input fans (front and bottom). None for output fan positions (back and top). The bottom dust filter is easily removable, I haven't tried the front.