THe one weird thing though, was as Happy Camper mentioned, there was a hiss on the outputs of the Hilo that wasn't present on any of the rest of the DACs. Again with more time in my own setup at home one might be able to fiddle with all the different settings inside to get rid of it.
I haven't experienced any hiss with my Hilo using headphone, TRS or XLR out, before or after level ajustments which I described earlier in the thread.
Both TRS and XLR have been fed into EAR Yoshino HP4 XLR feeding Sennheiser HD 800. Headphone out has been used with Sennheiser HD 800, HD 650 and beyerdynamic T 5 p so far.