My digital progress has followed a similar path. I started with a stock Node 2 then upgraded to a Node N130 with the LHY linear power supply kit already installed. The difference between the stock power supply and the linear power supply using the internal DAC was quite noticeable and well worth the upgrade to anyone considering it.
Then I added a Chord Qutest DAC using the coax SPIDF output from the modified Node N130 using an old Audioquest video (75ohm) video cable. I would have to say that the improvement using the Qutest was noticeable; however, not as massive an improvement compared to upgrading the power supply. There was improvement in the details that I've noticed in material that I know well. Recently I upgraded the digital cable to the Audioquest Carbon and the improvements were much more noticeable. The mid and high frequencies are more clear and well defined. Snare drums sound like snare drums, etc.
I've been debating an upgrade to a newer (and hopefully better) streamer but have decided to stick with the Bluesound Node for the foreseeable future. As stated in many posts, the OS makes a huge difference and the BlueOS does everything I need and want it to do.