What made you chose the DX220 over say a M11 or Hiby or anything else? Just wondering what made you go for the TOTL Ibasso DAP over something cheaper if you're coming from a smartphone and that's your comparison.
You have burned in the DX220 100+ hours correct? Burned in the Aeon's for 400+? Burn in is real and can and does change the sound. If you haven't burned both the DAP and headphones in you might try that before you judge. I know the Aeon's opened a lot for me after burn in.
I chose it based on the internet reviews. I was lurking for DX200, then DX220 was released and after reading positive impressions I decided to buy it. I bought DX220 and Aeon together, my expectation was "the ultimate portable audio setup". Haven't burned in them much yet.
DX221 (2.5mm output) + Aeon is quite unimpressive so far. The sound is overly thin (thin but not bright, energetic) Of course this can be caused by the pairing being bad rather than two devices being independently bad.
Dan (MrSpeakers founder) also thinks that AMP8 pairs with Aeon much better.