[user18]

I think it would be good to add them. Because if you don't, you'll just get people saying, "hey, you're missing soundstage... etc"

From reading other threads, headstage is a play on the word soundstage. Since soundstage should exist within an actual room, when people use the word soundstage to describe what they hear, they are actually referring to perceived soundstage. It's just semantics. Sort of like a 3-D drawing. It's not really 3-D and for some people it's a major pet pieve, but hey, to each his own.