Nice review on the K712. I felt they were great on the right system and were easily my favorite of the K7xx line which I have mixed feelings about, I personally always preferred the K6xx line. I had similar impressions of the HD 598 and HD 800, the "out & away" soundstage struck me as odd and a bit of a novelty. I personally hated the HD 800 for similar reasons as you listed, it sounded artificial and odd to my ears, it sacrificed too much for the sake of clarity.

I really love my K601. Could you please make a comparison between 601 and 612?

Well I was only able to compare the two briefly so it's just brief impressions, there could be other differences I didn't note at the time. They had a similar sound signature but the K612 having a fuller bass and more warmth were the most obvious differences between the two.