I had to come back and say that:
I hope I didn't deter anyone from buying them.
In my journey (I hate that) testing gear to see what was good or worked, I knew I needed new heaphones.
So I got some AKG K240 Studio Mk II (I used to have the regular ones), and they turned out to be the worst headphones I had in my life (like 2000000% bright, brittle, harsh, no punch).
Then I got a Tascam interface (I had/have a Uphoria Behringer 404HD), 16x08 because it was very cheap (16 ins) so I could record my drumset.
It was a total nightmare (drivers wise) and well, my AKG headphones didn't sound any better.
Then after the drivers nightmare got fixed (finally) I started hating Youtube videos a lot, because of their sound quality (this happened even before
getting the new Tascam interface).
Soooo, I bought these Beyerdynamic 990 DT Pro because the web glorified them (kinda).
And even though they weren't as bright/brittle/harsh with no punch at all, my experience wasn't any better.
After struggling with cables, connections, having bought a Yamaha receiver for my unused Yamaha NS244 monitors, I noticed that my Yamaha was distorting
the output, or so I thought...
Then it hit me: Maybe this interface is coloring the output (it doesn't help that a lot of Youtube audio content is bad, no matter the point of view, but bearable).
So I took out my Uphoria interface from its box (was planning on selling it) and used with it my new heaphones (DT Pro).
WTF is going on!!!! This world is crazy!!! My heaphones came alive, LITERALLY: Night and day!
They weren't brittle, bright, harsh (ok maybe from 200000% from my AKG reference, and yes, the AKG were used first with my Uphoria, so they sck ballz still),
but also got PUNCH, I didn't have to fight lows or low mids! I got convinced for a while because of my AKG and DT Pro (on the Tascam) that open heaphones were
destined to be this way, but nope, these DT Pro's finally sounded amazing (in comparison to using them with my Tascam).
So through my Yamaha receiver, I haven't heard them distorted, in fact, thanks to it I can EQ them a little bit down on the highs (-4), and still sound open not muddled
as if I tried the same thing when using the Tascam interface.
So, in summary: Tascam sckz ballz to the infinite (I have sworn before no never buy anything from them, but it was the cheapest option to record drums at the time),
DT PRo rock, Yamaha NS244 rock (to an extent) and Uphoria interfaces are indeed really good (maybe not PRO PRO PRO but you get the point).
All in all, it seems the signal chain does matter, but the fkced up situation is took me forever to find out... wasted lots of time (life) to find out... sigh...
(DT Pros has allowed me to hear stuff I didn't hear before even on Youtube videos, I almost sold them, now no way they are leaving my desk :P)