Soundstage can have a lot of factors. Yes, being able to isolate each part of the song so you can follow it. There maybe could be too much soundstage.
The issue is that open headphones do have great soundstage but at the risk of loosing a little PRaT as well as slam. So you have to have all the little parts of the package.
Soundstage is also going to be affected by your source and amp too. The recording process is really the most determining factor affecting soundstage.
Some headphones are even going to have a muddy little fog in one area of the soundstage, meaning the whole soundstage is not clear. Or even a character which seems to color the whole soundstage. All these things are not perfect but can be learned to live with if you like the other qualities of the headphones. There is nothing more boring than a narrow soundstage. It can take the life out of a stereo image and make it seem unmoving and dry. At the same time, when done right a soundstage gives the feeling of an alternate musical living space where you can spend a lot of quality time as different things are always moving and changing.
I agree with just about all of this - that's why I've quoted the entire post.
The only point I'd debate is "The recording process is really the most determining factor affecting soundstage"
It is a huge determining factor - and not given its due nearly enough - but IMO it's not "the most" determining factor
However, at this moment I'd be hard pressed to say exactly what is the single most determining factor affecting soundstage.
Because there are so many factors; so many links in the chain of recording & playback which contribute to that sense of depth, space, air, dimensionality, size...
