Hi,
Have several headphones at the moment.
Philips X2HR is one of them.
And I must say that switching to it after listening to the AudioQuest Nighthawk or Sennheiser HD700, it seems a little "thin".
But after 2/3 minutes, it is really enjoyable because to my ears it has bass without sounding "shady", has really "fleshy" mids and has trebles with no "sssshhhh".
I have even decided to give up the search for the ultimate DAC/amp thing.
I have a little bear B4 headphone amp (70€ I think) and I simply hook it up to the jack output of the computer motherboard.
And I tell my OS (GNU/Linux Arch-Based Manjaro distro) to play music using QuodLibet configured to use the ALSA output directly.
That has only one drawback : that jack output doesn't accept 88.2Khz files and so plays them about 10% too fast :-(
Overall, it might be the best sounding and thus, the X3 is awaited here
Regards.