I have done the same a/b with my nd5nxs vs ndx2 units into a NDS/CD555PS/282/Hicap DR/250 DR back end. Playing through the Naim app for tidal/qobuz, super lumina IC NDS to 282/HiCap to 250.
Based on earlier forum comments and pictures of the streamers side by side etc I was prepared for no difference. I started the trial with NDS as the streamer via Ethernet and Naim Tidal connect (sans Qobuz) then added my ifi Zen Steam/ MCRU 12v ps via Roon then the two more modern Naim units.
I was hoping I’d be very content to sell off the ndx2 and maybe even the ND5 XS2.
No question the ndx2 clearly bests the ND5 XS2 as a steamer into the NDS. The emotion cohesiveness and excitement of listening was very apparent. Is it worth the $3K CAN price difference used? Over a 5 - 10 year cycle I think so, but of course very personal decision.
Now it’s NDX2 vs NDS with CD555PS listening to see how different they present. (Started the journey with NDX2/XPSDR and the NDS was ++ better IMO.) Never thought I’d be considering the NDX2 as a streamer only, but in my search for the streaming solution best for the NDS and reading how others such as Simon has sang its praises with Chord Dave etc I tried and it does sound amazing:). Others have touted the Sonore Ultrarendu/UPnP bridge solution which I tried and just couldn’t get to work in my environment, although it would be ++ cheaper.
If my NDS ever fails at least I’ll have the ndx2 to fall back upon which will still sound excellent and I’ll be down a box! but I’d prefer things stay as they are:)