CMA400i sounded great to my ears especially with neutral, fast and clear headphones (T1 gen 2, HE-4, HD700, T90). It has a lot of power without hint of distortion, changeable GAIN, TRUE DSD processing without PCM conversion. Muting relays for power-on & power-off transients. USB isolation is great. DAC chip is top notch AK4490. Great low phase noise clocks. CMA400i looks great especially with transparent top.
I had a chance to compare it directly with pioneer u-05, aune s6 and ifi dac. It was like OK, but after I checked out cma400i it was like enlightment, at least with mentioned headphones. Punchy, with amazing depth, resolution, with a lot of weight and authority, focus, great tonality, attack and decay.
As I am great fan of companies like AUNE, S6 in my opinion had to let go in this competition. CMA400i was more like epic S16 from AUNE which is now discontinued regarding the sound (only DAC section of S16, because the amp is not so good there, amp in CMA400i is amongst the best)