Have you heard the 3003? I was in love with the 1p2 soundstage until these babies. They showed me how sounds that traverse the left/right field on the 1p2 are rendered in a severe fashion. Also, while the 1p2 soundstage is massive, it's like a halo - it's kept out at a distance. The 3003 soundstage is also very large, but sounds can be in any location outward, giving them a very immersive experience. The 1p2's soundstage is like a large onion, but sound comes from the very outside layer. In the 3003, sound can come from any of the layers in the onion. It adds quite a bit to the imaging accuracy.
You're right about not many headphones being able to break out of the congested soundstage mold. But there's a new era of IEMs now. They are getting better.