I think these would be great upgrades to the m80s. I actually sold my m80s to fund buying the X1.
Vastly improved soundstage with great bass and still a fairly relaxed sound signature. The X1 are also comfortable. I had to loosen its grip on my head a bit because i havr glasses but those velour pads are wonderful.
Can you make a more in depth sound comparison between them? Or maybe some else can? It will help me a lot and seems that I'm not the only one who interested in such comparison.