Given up on DAP. Will buy a LG phone and use it as DAP and a secondary phone.
Some folks @ YouTube made videos of using 250ohms Beyer cans with V30/40, should be adequate for my purpose.
My redmi 4s would barely output on the 770 Pro 80ohm. Asus 5z is ok, needed volume about 75% at least. They specify "24-bit/192kHz audio", so it probably has a decent audio chip. But can't imagine 250ohms being adequate on it.
Even on the usb x-fi, i think the amplification wasn't enough to bring out detail at low volume so i probably was increasing volume to compensate.
I would say use your existing phone and get a small inline amp.

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