I have employed the Warpspeed VIII with good results using the following equipment and my HE-6 headphones:
Sources - Oppo BD95 with diy Burson discrete opamp mod, Squeezebox Touch, MacBookPro.
Amps - Schiit Lyr, Threshold CAS-1, Threshold A400 w/ factory upgrade to e Series circuits (e.g., optocoupler bias circuit, etc.), Conrad Johnson M50, B&K ST202, modified B&O ICEPower ASP1000 monoblocks. (I have also inserted a vintage CJ and ARC preamp in the chain without issue.)
The Warpseed has extremely fine grained resolution from dead silence through barely audible to max. Of note, the BD95's output impedance is around 80 ohms and the ASP's input impedance is 7.5k. With only the Warpspeed between them they match up with no problem, as do the other amps.