I tried the HD800s with a DacPort LX and couldn't listen to them. Then I realized that the headphone was simply showing me how the LX sounds—I've always found it a bright DAC, but most headphones roll off the top. The HD800 doesn't—it reveals everything—so the trick is to find a combination of source and amp that doesn't err on either side of the frequency spectrum. In my system, replacing the LX with a MHDT Havana solved the problem. By themselves, I don't find the HD800s bright or harsh in the least. To me they sound balanced, neutral, and correct.
You are right the HD800 is a balanced, neutral headphone but its a very bright with my current setup. I think it's my source the M-Dac will try with another DAC.