I second the general opinion about your server. Your system is excellent, the weakest link is the Root Nucleus.
I'm a big fan of Audio Note (my system is all AudioNote). My Server/Dac was not. I did audition the AN 4.1x dac with room nucleus at my home and it was a disaster. Not impressed by any means so did not spend the money. A couple of months latter visited the local Dealer for an audition with a Inous Statement and a HiFi Rose as servers. Completely blown out. So much so that I purchase the Dac, waiting for it to be delivered with a Rose as server.
I would not change your Dac before testing a dedicated server in your system.
Best