Just got a new Bluesound Node. Very disappointed!

Something weird is going on....  my Vault 2i ( pretty much the same as Node) was connected to a NAD M51 and it sounded fantastic.   I would do a hard reset on the Node.  The BS / M51 combo was very balanced top to bottom.    Subterranean bass and smooth on top.   It should sound great with that DAC.

I would agree, your Node has issues of some sort. A reset might do it, easy enough to try. For the $$$ the Node (especially the current one) sounds really good. 
 

Important: Audio clock trim

- BluOS uses small adjustments to the audio clock to maintain glitch-free audio synchronization. Disable this when using an external DAC that cannot cope with these adjustments.

There is a setting that you might like to change to see if it makes a different in term of sound quality

Bluesound has outstanding customer service. The IT guys helped me a couple of times. I can't imagine they couldn't isolate and fix your problem.