I also agreed that paring NDS with a more recent streamer like ND5XS2 or NDX2 is a worth while investment if you are like me that the ND555 is a bit too out of reach.
I currently have the NDX2/NDS/555PSDR combo and I am very happy with the result, particularly on the TIDAL/Qobuz/Spotify streaming side. Although it still feels overkill using the NDX2 just for the tiny streaming board and disable the rest DAC part where it excel over the last version. This means pairing it with the ND5XS2 making more sense.
my initial plan was to ditch the NDS and use the NDX2/555PSDR. Although the SQ in NDX2 has improved a lot over the old NDX when I first auditioned, but still, they are just still not on the same level as the NDS despite it is an old product.
Also a fun fact to note that I compared the NDS/555PSDR with nDAC/555PSDR using a CD5XS. Although both DAC are pretty much on the same playing field to my ears, the NDS sound more Naim or musical or cohesive than nDAC. My personal assumption is the nDAC was designed to be paired with different sources in mind, including non Naim sources, so it may need to have a more neutral character, and to my ears is a little bit sterile if I have to compare it vs NDS. Bottom line is both DAC are great in SQ, they are just different with their own sound characters. If you don’t have a NDS for a critical A/B test, you will certainly enjoy nDAC if pair with a more recent source like ND5XS2/NDX2 especially mDAC is much cheaper than an NDS.
Also want to share that although I did start with using an XPS with both NDS and nDAC before, the change to 555PSDR, even though is a huge investment even on 2nd hand, it worths every single penny. I believe that is what/ how these DACs were designed and tuned to be pair with in the first place, Naim just offer other alternatives for people like me who need to “work my way up” slowly to finally afford one to see what these DAC can really do if a higher quality power supply is used.
Always happy to see someone still hanging on to their NDS , which in my opinion is a great and reasonably priced flagship streamer back in the days vs the price point of the new current flagship ND555.