Thanks for all the replies. Just to clarify, my post was not intended as seeking advice. I just want to know if soundstage is really speaker dependant because in my case it seems it is not. No matter where I have speakers (by front wall or extremely out in the room as right now) stage appears on the front wall. I actually like that.
And btw in this position soundstage is very wide, almost 5m, it is as wide as "projection of speakers from my point of view".
I'm not native speaker, sorry if it is hard to understand me sometimes.
It is speaker + room dependent. The radiation pattern of your speakers changes how the energy interacts with your room, and those reflections + the direct sound make the "soundstage". Those same speakers in a different room will sound different, different speakers in the same room will sound different, changing the material of the walls would sound different, etc.
In order to understand this better, you could look at the energy time curve of your room. It allows you to see what percentage of acoustic energy is arriving in a given time slice. You can also go further and look at the decay slopes of individual frequencies.
When you see "estimated in-room response" shown in reviews, this is based on a typical rectangular room, with a typical level of absorption. Things like a slanted roof, low absorption, high absorption, or an L shaped room would all make that data less accurate.