Just to add my two cents: In the true sense of the term the Hugo₂ actually does have an amp – a single class A line output stage with extremely low output impedance and enough power to drive headphones. But it still lacks an additional headphone amplifier, so it's a more direct signal path than with conventional DACs with headphone outputs.
Now there are people who use a «better» amp with the Hugo₂. Ignoring that you can't bypass the «worse» internal amp, just complicate the signal path. Now some people like the added harmonic distortion (© Rob Watts) and mix them up with better dynamics and larger soundstage. Which leads them to the notion that the Hugo₂ be an excellent DAC with a mediocre headphone amp.