I really liked the 8400s when I had them at home and recording some snippets BUT I didn't like them for just listening and enjoying music. Too tilted up-top, too cold. But for recording and probably mixing they should do excellent.
I'm actually surprised no one has mentioned Shure SRH940s!!
Yes they are bright and their bass attack is lacking (i.e. not boosted, no slam) but I don't doubt they'd do great in that setting. Personally I preferred them over the KNS.
KNS8400 is cold, not sterile-sounding but clear and analytical. The treble is crisp, but not too much. In both respects, it reminds me of K70x.
SRH940 has a good soundstage for a closed model, unquestionably better than KNS8400, and resolution is comparable to it. I couldn't take the uncomfortable hot highs, so I decided not to buy it.