Just came accross good reviews of Amp2:
http://kopfhoerer-lounge.blogspot.com/2017/05/iBasso-AMP2-Review.html
and Amp3:
http://kopfhoerer-lounge.blogspot.com/2017/10/ibasso-dx200-amp3-review-english.html
no sure if those have been posted here before...
Yup, they've been already posted here, and they've also been re-posted in the Head-Fi Head Gear review section.