As others have said, a quality copper cable will cure most of your HD800 ills. do not put silver near those headphones. They are already extremely detailed and Frank can steer you in the right direction with a good copper cable to smooth out the high end and increase low frequency response.
I have been using my new balanced silver widow with my HD800's for the last few days. Very smooth & extended highs and powerful, deep impactful bass. No smoothing of treble or low frequency boost needed.
If you have no issues with the quantity of bass or the quality of treble with the HD800's then you don't need to avoid a high quality silver or silver/gold cable.
Edited by nigeljames - 4/30/13 at 12:45pm