Where should the vocal image be?

but what piece of equipment and it could include speakers, is responsible for the imaging / soundstage

I would venture to say it would be the speakers.  Then followed by the recordings.

It's could be quite subjective as I would prefer the vocal to be at least mid way between the listener and the speaker plane.  I understand this would trade off soundstage depth.  This leads to another related topic as would you prefer that "they are there" or "you are there."

OP I hope you found a baseline from all this???????????

I think one thing we can agree on is that there are a few variables.  Once you have an optimal setting, most likely it's the recording that dictates where the vocal image will be placed on the soundstage.