ES9023 is "all in chip" and "direct output" DAC but offer good quality.
ES9018 is pure DAC chip, with analog filtering output stage and +/-12V linear powered OPAs
This offer more powerful output signal and can be felt in sound, even if ES9023 is already sounding good.
The other difference is Linear power supply :
ES9023 has integrated linear regulator, but limited to 2A / 4 Peak because no heatsink
ES9018K2M version will have separated linear regulation board, that could offer 3-4A continuous / 5A Peak
We also plans to add "Power" USB output on K2M version, to supply external & not self powered USB HDD