For what it's worth, I've been listening to my HD800S for the past two months running directly from the Hugo 2. Even though there is plenty of power, it's a completely different experience running them off my new Woo Audio WA22, fed by the Hugo. Beyond the tube flavor it seems to expand upon the best elements of both the Hugo and the Woo providing a new unique signature.
People often ask for recommendations for amps to pair with the Hugo on this thread. The typical response is that it's not needed. In general, most headphones do not "need" more power than the Hugo can deliver, but mixing and matching gear to personalize the sound signature is still a valid approach to take. It's a hard one to answer unless you have the same gear and taste, but this is not a one size fits all hobby. That said, the Hugo on it's own is a great option, but not the only one. The Hugo's neutral and highly transparent signature can pair very nicely with the right combination of tubes, kind of a yin yang thing
. I would imagine there are other amps that can add their own unique qualities to the mix as well. If your just looking for more of what the Hugo already offers, then I agree, an amp probably won't add any value. My HD800S are not the hardest ears to drive, but they're not the easiest either, and I am no where near maxed out when running direct from the Hugo.
For a mobile solution, the Hugo 2 on it's own is probably the most practical but there are other options. Sticking with the tube theme, I travel with the Hugo 2 and Woo WA8 which does not deliver the same impact as the WA22, but it's still a great flavor and a nice option for variety. ALO's CDM would probably be a nice pairing as well.