mechan :
Thank you for your kind words.
Yes, we're quite familiar with the tracks... we essentially picked our favorites in a few genres
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One more thing to add to my original comment...
I think most modern DAC chips have exceptional performance compare to the old ones. So the crucial part of audio quality comes from the Inter-stage & Output Amplifier, which determines the majority of the device's sound signature. With that...
So after comparing the ALC898 (on the P8Z77-V Deluxe) to the Asus Xonar Essence One using HD650, there is a clear difference in the presentation. There's more loose low bass on the ALC898, not as tight as the Essence One. This is probably due to the Integrated Amp on the SOC having 2 Ohms output with a max of 1.1Vrms swing. This causes the bass to be under-damped and out of control. Whereas, the Essence One has 7Vrms from +/-12V rails.
Also, there seems to be a faster roll off in the upper highs on the ALC898, making it seems somewhat warm compare to the Ess One, and not as bright. Ess One has a lot more crisp in the highs.
Overall, the ALC898 sound stage is not as wide, and the music was kind of thin, not as many layers. The music lacks impact, lacks excitement on the ALC898. The transient is slow, most likely due to the weak internal opamp in the ALC898. And if you read reviews on the high-ohm headphones, you'll find that they need higher Vrms to be able to fully drive it properly, otherwise you headphone would be under-powered. And you won't hear the full range of sonic experience that they're designed for. As for the HD650, some say 3Vrms is the norm to properly drive it.
I'm surprise your blind test didn't reveal that, even with the HD800. It should be quite obvious that the ALC889 isn't capable of driving such high impedance headphones. You can crank up the volume to make it loud, but it just won't perform well pairing with such weak amp.
* The Essence One was mod with replacing all the NE5532 with LME49720. It gives it more of an analytical sounds. And it pairs quite well with the HD650.
* The ALC898 actually has slightly better specs than the ALC889