So I definitely get the whole K1000 thing. Originally when I listened to them at Canjam, I thought they were neat, but nothing jaw droppingly stupendous. Now I see that, like the O2, the K1000s are one of those delightful cans that just continue to unfold goodness unto you throughout extended listening sessions in one's own rig.
Of course the proof is in the puddin', and the puddin' in this case is a delicious and true midrange. Tweedy's vocals on the Sundazed YHF vinyl are out of this world, same for EJ's vocals on the DCC Greatest Hits. Guitar crunch and solo-sheen are gorgeous.
There are some negatives. First, the tight fit on the skull. I'm a bitch when it comes to headphone comfort. I still haven't shut up about the K701 and I sold them two and half years ago. Having said that, the tight fit is not awful, just not super comfortable, and at least its not an idiotic design like the K701. Still, nothing beats the comfort of a plain old adjustable headband Senn HD series.
Second, I'm still experiencing some fatigue after an hour or so of listening. I'm experimenting with toe-in to see if I can reduce this.
But the above complaints don't change the fact that the K1000 has a midrange that can make men do stupid, stupid things. Not that I'm going to buy a crazy dedicated amp for the K1000, but I see how someone could.