Ok, I took the plunge and ordered the AT AD700's and I'm very excited. Yes, they have almost 5/5 stars out of 200 reviews on amazon but that's not at all the reason I ordered them.
I read all the forums about how great they were but I was looking something more specific and I found it. Skip252, very in line with what you said.
The professional review I read said the following:
"Another thing that the AD700's did well was separate each instrument instead of blurring them all together into a sonic blob. They also did something that many headphones, even expensive ones, have a hard time pulling off -- creating a semblance of a soundstage. I could not only pick out where the instruments were located, but I also got a sense of lateral space and layering. This is something special in top-flight cans, so hearing it from the 'AD700s was surprising."