Audiophool nonsense regurgitated by the AI.
That's the wrong impression to get.
Headphones improving step by step as you get beefier and more expensive DAC+Amps to drive them with is a complete myth, born almost entirely from sunk cost fallacy, confirmation bias, and a lack of controls when comparing.
The fact that you hear no difference between the DX1 and onboard audio instead is a testament to the fact that
A) DACs and Amps are no witchcraft and have been audibly perfect for a long time and
B) The Kithara is an easy headphone to drive and performs at its best used with most any headphone output.