With so many HD800s on the classifieds now, they gotta be competitive with each other, and as a result I keep seeing lower used prices for HD800 every day. It used to be you'd find used prices in the 1,200-1,100 range for the HD800, but now I see them going for 850. At 850, the HD800 is a steal-- even compared to 250 or 300 for the HD600 or HD650 (which are also terrific deals).
People love to complain about the tuning of the HD800, but the reality of it is this:
1: the HD800's super large and open earcups provide a very natural and comfortable fit on the ear. better than HD600 or 650 in this regard, and the best I've personally experienced.
2: the HD800 has a super large soundstage, it's the largest I've experienced, and you can't EQ a good soundstage with other headphones.
3: the HD800's 6khz peak can be greatly tamed with 3 dollars and 30 minutes of your time
4: the HD800 easily takes EQ. Its bass naturally goes rather low for being an open dynamic, and with a good low-end EQ, it can be made to sound powerful. You can't EQ the low-end distortion out of the HD600 or 650. the treble is also easily EQ'd down as well. the mid-range is very smooth, so won't need much EQ.