It really comes down to these aspects:
1. the headphones
2. your preference
If you are using a high impedance dynamic driver headphone (Sennheisers, ZMFs) or a power-demanding planar headphone (Abyss, HE6, Susvara, LCD4), it might be advisable to you use a suitable amp in the chain even if you are using Hugo 2 as a DAC. But I have seen some people driving the Sennheisers, ZMFs, LCD4s out of a Hugo2 and be perfectly happy.
Non power-demanding planar headphones and Low Impedance dynamics might not benefit a whole lot from a separate amp, but some people still prefer to drive them from an amp over straight out of Hugo2.
And then comes your preference. Some see Hugo2’s tonality as neutral and appreciate its technical brilliance. For me and many others, we find Hugo2 bright, analytical and sterile. Although we are able to hear it’s technical brilliance, the cold tonality just doesn’t let us enjoy the music.
I used to have the Hugo2 as the DAC in my desktop chain. It really didn’t make me come back for more. Then I got to try a Cayin N8 as a DAC in my chain and I instantly knew that I was going to sell my Hugo2, although Hugo2 was definitely better than the N8 in many aspects. But the N8 being the warmer, fuller, smoother sounding device, it made me enjoy my music way better than what the Hugo2 did.