So I just got a pre-owned C&C X02 from a fellow member of a local audiophile community. He used to own a K701 too.
The most significant change I noticed is the sound became warmer and fuller. Bass is thumpy, and soundstage is a tad wider.
Detail retrieval is still the same, though I've noticed some instruments I never hear before in one or two tracks.
Source is Cowon J3 with mostly 320kbps MP3 files of varying genre (rock, jazz, jpop, metal)
By the way, my K701 doesn't have the doughnut foams inside the pads anymore (I got it pre-owned, previous owner says he lost the foams). Serial number 14639
I'll try to post a more detailed review in a few days.