I have detected no 'sibilant treble' whilst listening to my headphones. The only thing I did was to pick a headphone, amp which had been reviewed with the 800's.

Not sure if this is of any help but I am extremely happy with my set up smile

Cheers

Shaun

DSP6000, 5500 centre, SW5500. Kef surrounds. G61R, HD621, MS600, MC200, G55, Lumgen,Oppo bluray player, Bluesound Node Icon