thank you for your patience yakuman.
now what is left to me is to decide between the define C and one of the BQ cases.

btw what can you sat about meshify c ?

I presume you are talking about the washers that go under the 'stud nut' spacers on the original Kotetsu, not the plastic spacers on the Kotetsu Mark II? (I just looked up both their manuals to try to work out what you were talking about.) Is there any further documentation of this issue somewhere?

You're welcome!

Gamers Nexus review that I linked earlier should paint a clear picture: Meshify C has better temps due to ventilated front panel (no surprise) vs Define C's solid panel, at a cost of higher noise. However, once the Define C's front panel is removed, it's actually cooler temperature-wise. I also didn't like at least 2 things with the Meshify: 1) the logo on the front panel bugs my OCD and 2) dust would be a pain to blow out to clean in all those small ventilated holes. This was before I thought about removing the panel for better airflow, so in hindsight this may not be a problem now.

yes, i read now a review that tested both of them and the conclusion was exactly what you have wrote now.
so, i stayed with the decision between define C and BQ silent base 600.

It's the opposite. The metal spacers are the ones you should use. The plastic spacers are the newer ones that were absent from the earlier production batches. I'm glad I found this before installing the Kotetsu from a fellow forum member stumbler here: viewtopic.php?f=8&t=69254 I don't know anything about the Mark II version.

if i'm not wrong i saw that in the define c ( and maybe in all fractal design cases ) the ssd drive attached to the case wall.
doesn't it make the ssd warmer then if it would be more open to the air ?
my current ssd drive is Lying on one of the drives "shelves" inside the p-182.
not ideal but it has more sides open to air.

SATA SSDs' casing act as a heatsink in a way. They're less prone to heat compared to M.2 SSDs. If you're still concerned look at my other post: viewtopic.php?f=15&t=69991&p=608308#p608308

In my R5 PC I removed all drive cages (same with Define C) and just left my Samsung 840 EVO lying on the case floor without obstruction. In my Define C I mounted my Samsung 850 EVO diagonally using the SSD plate behind the motherboard and while it's apples to oranges comparison, I don't think there's much difference in temperatures.

I think at this rate you should update the thread title to something else as we're jumping around topics all over the place

ye you i right.
do you mean ti update the name/subject of the thread?

i will use in the new case one m.2 ssd , and one hdd drive.
i'll try also to remove unnessesery parts in the case.

I discovered a new source of noise: hard drive vibrations. This never occurred prior to me removing the front panel. It took weeks before I narrowed down the root case and remembered some users in the past had the same problem with other Fractal cases: the bottom dust filter. Without the front panel as reinforcement to hold the front part, it's prone to vibration. The fact that it doesn't always happen made it harder to discover. I haven't thought of a solution or workaround yet.

interesting and a bit worrying.
i'm not planning to remove the front cover of the case.
think i don't need it for more airflow.
i'm working now with a totally closed antec p-182, although i have on it an upper fan which i'm not sure i'll add to the fractal design.