I agree that they are different. The K1000s are the kings of getting the music out of the middle of your head. They create a very speaker-like experience. The downside is that you share the experience with everyone nearby, even moreso than open back headphones. The HD800 does a very good job of getting the music out of your head too, I'd say second best of the cans I have listened to. But they do lack a bit of space and air that the K1000s have. The slight downside I find with the K1000s is that you need to pivot them in a bit from the position that gives the best soundstage to get the best bass or they can sound lean. The HD800s have a nice full bodied sound.
They are both rather odd to wear and quite different feeling. The K1000s only clamp on your head, not over your ears, and that creation of a smaller pressure point on the head was a cause of complaints by some folks at the meet. The HD800s have really huge earpads so they really spread the load evenly, but they can feel a bit claustrophobic and overly warm as they trap a lot of the heat coming off your cheeks. I would strongly suggest trying both on to see how they work for you. You look equally silly wearing either one, earning top geek style ratings.
By the way I can't say this on the Head-Fi forum without looking like I'm trying to advertise, but I would hope that folks would consider the amps that were running the K1000s as partly responsible for the comments about the K1000 sound we get at meets. I consider the Paramounts and K1000s a system, and I don't really feel that the Ks will sound the same with other amps.
