@yyzsantabarbara - so, I can test the X1 output. I am not using PLink. Just USB vs Ethernet. I did AB testing with the X1, the Soulnote and the MPD-6. I had two of the three connected to my preamp at at time. Both connected to my Oladra, X1 via Ethernet direct connect and the other DAC (Playback or Soulnote) via USB.
the Soulnote and the X1 sounded VERY similar. The MPD-6 is a clear step forward in virtually every way, even using an inferior connection. It sounds bigger, more detailed and more holographic than the X1. The soundstage had more depth and height/width. The X1 is excellent. The MPD-6 is just better.