Roscoeiii
1000+ Head-Fier
Bigger battery and more power are givens. I don't find those being worth $400..
If bigger battery, more power and additional features aren't worth it to you, and you don't hear any significant differences on your gear, then save your money and move on.
Having Sensitive IEMs like Andromedas and more power hungry planars like HE-5LEs and HE-560s, it is very difficult to find a single amp that can drive them well. The Micro BL does that with aplomb and there are headphones in my collection that benefit from the 3D and XBASS.
I think most of us here trust iFi's responses here and on their own webpage over what is on an Amazon page. And I think most of us here are pretty clear on the battery charging situation and accept that state of affairs as the best that could be achieved for a device with these performance capabilities.