I own the 860x for more than a year now, and have used it with and without pre-amp. My pre-amp was a BAT Vk-40, the BAT sounds Beautiful! but let me tell you when I tried my Wadia 860x Direct to my amps Oh man, incredible! Details,Details. I play lot of different flavor like smooth jazz, vocal jazz, Hip-Hop, Latin(jazz, salsa, merengue) oh yeah! you got to tried Paquito D' Rivera Tropicana Nights SACD format, Stunning!. I did match the output voltage of the Wadia 860x to match my amps and play at a reading of between 80-96. Sounds Amazing! My setup is:
Wadia 860x ( I want to do the Wadia Statement upgrade)
Krell KMA-100 mono block.
Icon Parsec 3-way speakers.
AudioQuest Anaconda 1.5m.
AudioQuest Dragon HL 1m two pairs.
3-Elco Power cables.
Peace!