A couple nights back, I brought my Mk I to Sgr's house, and we A/Bed it against the Mk II in his system (which is sounding very impressive, btw). All present agreed the Mk II is a very noticeable improvement, particularly in areas such as detail, spaciousness, imaging, and clarity: the Mk I sounded sludgy by comparison. Though I'd have to listen more for a fuller description, I'd say the Mk II retains the relaxed non-edgy feel that I like in the Mk I. I suspect that a majority of (satisfied) Mk I owners will think the upgrade money well spent.
John
John