Dynamic, as I've been trained in piano/music lessons since 6, has always been about controlling the overall loudness, ppp to fff per say. Different level of dynamic of course can be achieved by finger attack speed on piano or bowing pressure/speed/angle on violin and other techniques... For me, dynamic is simply the range between the lowest volume and the highest volume.
I have also realized that when it comes to HPs, the perceived dynamic is greatly affected by what you mentioned, soundstage, HP speed...these factors make the argument a little too subjective to discuss clearly cuz we all hear/perceive things very differently.
Btw, I love scotch but prefer tequila. New bottle last nite too.
Hmmm.... I like tequila too :D
I'm on my fourth large one and I've changed my avatar to the Hoff... I just can't be serious now guys
But if I could just squeeze one last little bit of sense out of my soon becoming inebriated brain, it would be that 'dynamics' is one of those terms that is not easily understood by a lot of head-fiers and this is a good healthy argument. And you've just described what 'dynamic' is very well there bud imo.