I just did a comparison with the K702, K712, HD800, and LCD3(f). I used TRS single ended output from my Eddie Current 445 amp and stock cables for all but the HD800 which has a hard-wired Wire World cable, (with a single ended adapter). I listened to CD's
Vivaldi Farwell Concertos, and a
Haydn String Quartet.
You are right the K712 does sound warmer compared to the K702, but the detail in the treble is still there, IMO. The treble detail is more obvious in the K702 because the midranges and bass are somewhat lacking. The K712 had a richness, depth, and saturation that the K702 couldn't match.
Comparing the K712 to the LCD3(f) was again a step up in bass extension and a richness in tone. The LCD3(f) had better separation and detailed instrument placement, but the difference was not as great as I would have expected for the $1,400 price difference.
The most surprising finding was that the K712 sounded most similar and actually better than the HD800. The K712 had all the detail of the Senn, AND better bass extension. There was a kind of subtle musical quality to the Senn that was perhaps better than the K712, but the separation and detail were clearly better on the K712.
Hope this helps anyone out there thinking of getting into a K712. I can't see how that would be a bad decision . . .