High End amps i would recommend..
Woo Audio WA2 (for tubes)
Sennheiser HDVD800 (need to run balanced)
Auralic Taurus MKII (Need balanced too)
Violectric V281 (Balanced as well, has optional DAC)
Schiit Ragnarok too perhaps? Havent tried this one yet
All bar the HDVD800 are standalone amps which would require a DAC too but are very good amps for the HD800 in my experience.