I couldn't hold myself and did some more Stellia listening today. Basically my idea was to sell the Ultrasone J25 and after setting up the HT system to buy a Stellia. Again I was quite impressed with Stellia. But, interestingly after a long listening session on my WM1Z and putting on the J25, Stellia's Focal character -mid-forwardness- hit me. Although not as much as Utopia, it is still there. There is a lot of Ultrasone bashing here and also at SBAF, but they did it right with the J25. I always let my wife do the blind tests, as she is a musician and initially she didn't like the highs, but was very impressed with the bass of her own studio recordings. After 2 months of using J25 with EQ, I decided to remove the equalizer and, wow, the highs were much better. Also confirmed by the wife that they are now milder and more listenable with treble rich music. Still I think there is more treble energy than neutral, but nothing you can't get used to very quickly or can't fix with a bit of EQ. When I compare the two J25 is easier to listen to for longer periods, both because it is lighter, has less clamping force and mids are more laid back and does not make you tired easily.
I just have to accept the fact that the Stellia will not be able to replace my J25 "sonically". But J25 needs babying. It is simply too fragile to be taken to the office or put on the desk. This is where Focal's tank comes in. It is very robust and would survive a commuter's life.
If I sell the J25, I guess I will miss it. I will sleep over it once more, but looks J25 stays, soon to be joined by Stellia: The second best closed back HP I have ever heard. But someone has to leave: WM1Z! To be replaced by DX220 (if it has Bluetooth receive mode, which I believe it will) later.