FWIW Here is un update on my experience with the Topping DX3 Pro. The Topping did not reproduce some of the harmonic content of instruments accurately. The sound itself is fine, for a relatively inexpensive DAC/Amp. However, when I A/B tested it with my Apogee One, the sounds with the Apogee sometimes included additional overtones, making it a more well rounded, accurate sound from some instruments. I first detected this playing my favorite songs on the Topping, at first happily listening along. I A/Bed with the Apogee to verifying what I thought I was hearing, both at same volume. In one song, the sax was coming off a bit "boomy". On the Apogee, this was not the case. There were additional frequencies of the sound that brought out more its character, that of a sax. This difference was obvious to me. So I have returned the unit.
The DX3 Pro initially sounded good until I played songs that I have used to test other such units years in the past. I have the sound memorized, having heard the same music literally thousands of times. I know how it sounds with better DACs. The DX3 still faired better than the Apogee One in other regards, but not good enough for me. This experience of mine belies the tests performed by Amir. So the only rational explaination is that V2 differs from V1 of this unit.
In its place, I have purchased an Apogee Duet for the Mac and the iPad. This costed me about $330, normally over $400 used. It is over $600 new. It is an actual audio interface that I will be using for my recording of the music I play with my electronic synthesizers. So it will be doing double duty for me. The sound from this unit is quit impressive. There is just a "touch" of sibilance on a couple songs on one album. If this happens on other music, I may end up using a pro software dynamic equalizer for this that I should still have, one that came with my recording software.
Now I have come full circle in my search for a DAC that can do as well, like the Duet, but at a cheaper price. I have failed. So now I am back with my Apogee Duet. I am selling the Apogee One. No close comparison between the two.