Actually its quite a feat to get a 50mm driver into such a small package... I don't know any more low-profile fullsize headphone.
I tried the XS yesterday, still not for me: the cups just don't sit correct for me and they would hurt me in the same way the m-80 did. Plus isolation is problematic as they tended to loose contact when moving my head. But when I kept still it was quite impressive what they put out given their minuscule size.