Hmm…yes!… kind of.
Ok, I did say in my very initial impressions yesterday that the perception of soundstage is an interesting subject, because people's perceptions sometimes seem to vary a great deal. Add to that the not so infrequent parroting, parroting... and yet more parroting (read: many people simply regurgitating what others say)…
So, several people have described the HD800's SS as being very vast. I don't find it that vast, tbh, but it's certainly very open, and I think this is often more dependent on the album you happen play—how it was recorded, placement of mics, etc—, your state of mind at any given time, and other variables.
Okay, then, since you put me on the spot, here you go: to me, if the HD800 is, say, a 10, the K3003 is a 9 and the ER4S is a good 6 (or 6.5).
One last thing I think I should mention: I believe I have a perfect fit with my 4S, ie I do hear the bass very, very clearly, hence one reason I don't really want any changes there (at least at this stage). Change the fit / insertion (I've tried that already) and the 4S sounds off, really off—never mind soundstage, it's just really off, thin, bright and severely lacking bass. I even listened to some Kanye West on my 4Ss last night and there was a bit of brain rattling, or so-called rumble. Why mention this? I've noticed that SS perception has a lot to do with how frequencies blend, among other things.
On a side note, have I mentioned that detail retrieval is simply superb on the ER4S?