Yes, you can use the USB as an output to a DAC--that's what I do, but this only became available starting with the Node 130, so the 2i or earlier models won't do that, if I understand correctly.
I'm using a Denafrips Ares II DAC, and I think it is only marginally better than the DAC in my Node 130. I suspect you have to go further up the Denafrips line to get a significant improvement over the Node's DAC.
The addition of the Teddy Pardo LPS to the Node made more of a sound quality improvement than the Ares II does. I think the Pardo people say it elevates the sound quality of the Node to the level of $2000 streamers.
Yesterday I listened to a few YouTube comparisons of the Node X and the Eversolo AM6. Based on these reviewers' impressions, it sounds like the Eversolo might be more detailed and brighter, so a good match for a laidback-sounding system. I hear live music as not so analytical, detailed or bright, and I think the Node provides a more natural, "musical" presentation than some analytical and detailed components do. I have compared Node hi-res streams to the same CDs and LPs, and often the streams sound just as good.
I also wonder if the lack of a graphical screen on the Node is actually a plus; if the electronics needed for a screen might detract from sound quality. I have two universal disc players that have controls for disabling the video electronics for improved audio quality. I have heard the improvement in deep bass when disabling the video. The info provided by such screens is available on my smartphone when I'm using the Node, so I think that is more convenient anyway.