I hesitated to respond to this but after listening to my NDX last night for 3 hours I thought I’d add some balance. I’ve had my NDX for 18 months (serviced & screen 2019) and use Spotify connect. Ive listened to more different music in those months than over the last 10 years. I’ve thought about adding an XPS (Or alternative) maybe three times In that time and each time after an evenings listening decided against it. The thought in each case came about simply because I had the cash available and not because I felt the sound needed improving. The decision not to spend it came about each time because I ended up feeling that the NDX sounds amazing on its own. My LP12 doesn’t get a look in at the moment. That might change but the NDX is staying as it is.
I have found that adding a power supply to every Naim component I have owned/heard made a positive improvement. Some marginal, others huge. Cost is sometimes prohibitive but buying used is an option with Naim. The 555 PS is much better than the XPS on my CDS3, active 250s and Nac 52.
I agree MKL1. … keeping focused on NDX, when I had a CDX2 I added an XPS & the improvement was probably the most dramatic I’ve experienced with PSU’s, more bass grunt/feel, better imagery, top end, detail & musicality.
Then I moved to streaming with an NDX & sold the CDX2 but kept the XPS.
I first tried the NDX on its own power supply for a few days, then added the XPS. Yes there was an improvement but nowhere near as dramatic as it was with the CDX2, its more refined & detailed & I wouldn’t be without it, but in VFM terms … ?
How many 555s is that?!
Have you tested this? I haven’t heard those two setups side by side, but having heard them on various separate occasions my gut feeling is that the NDS would be the winner.
Interesting.
I have an NDS powered by XPS-DR, I have not heard it powered by a 555 but to say it is handicapped without is unqualified and to my ears none sense. Some don’t see others’ perceived improvements in SQ offered by higher end kit to be relative to the associated extreme costs. I auditioned both and an NDS with XPS-DR easily and noticeably out performs an NDX2 in SQ and costs a lot less
I concur with ChrisSU - the NDX2 benefits from next gen streaming capabilities but the NDS has the top shelf DAC (same as N-DAc that many NDX2 users think offers the NDX2 a lift in SQ), has no inboard power source to pollute and has remote sprung chassis - super as the NDX2 is it isn’t close to the NDS. Adding a 555 to an NDx2 may negate a polluting power source but can’t improve the DAC etc. As I mentioned previously I auditioned an NDS powered by XPS-DR next to a bare NDX2 and it was way and above superior, adding the 555 to both I think would actually widen the gap - music signal is all, you can’t add to it by removing noise but less noise will allow the better signal to shine
Adding an XPS Dr to my NDX was very worthwhile. It reduced the digital ‘glare’ that the NDX exibits when bare, although it’s easy not to be aware of that until you hear it with the upgrded power supply. I’ve also heard an NDX/555 too but I would take an NDS/XPS DR over the lessor streamer with teh better power supply.
I did speak to Naim as to whether NDX/XPS DR is better/worse than the bare NDX2 and it was felt that they would be very similar. I’m therefore concluding that the newer model is a power supply better than the original NDX. This makes an upgrade to an NDX2 a great option as you get the newer streaming platform and save a shelf.
I eventually changed to an NDS/XPS DR which was excellent so I agree with @JonnySidemouth that it’s a super source. It’s now powered by a 555DR which is even better. Adding a Roon bridge has enabled me to overcome the shortcomings of the older platform meaning I can stream QoBuz.
You can find NDS at bargain price, as many owners are moving to N555, no matter the depreciation of their NDS, NDS is a great machine, closer to N555 than NDX2: its dac is superb, has very fast CPU, much better than the one on NDX.
Adding a PS to your NDX for sure will improve the sound, dramatically.
I haven’t actually heard these 2 units side by side, which is why I was making more suggesting than making a definite statement.
You could very well be right that the NDS would still sound better, but I would suggest that, if affordable, the NDX2 most likely sounds close enough to the SQ of the NDS, to not invest money in older, discontinued technology.
I, myself, would definitely get the NDS which is even less cost, but I can’t get Qobuz in Canada and that wouldn’t apply to the rest of the world. Our politicians here like to keep our status as more of an outpost, y’know …
I exaggerated a bit Jonny 
While I have no doubt adding a power supply will improve the sound, I’ve been very impressed with my late-model NDX-BT which I use at my office/shop. I feed it with my UnitiCore and Qobuz (yes you can do this) and I find myself totally satisfied with the sound. Supernait2 and Warfdale Linton’s seem to be the perfect pairing for this first generation streamer.
If you can find a good price on a 555PS you’ll get a pretty significant jump in SQ from stand alone. Then you’re a small jump in $$ to get a s/h NDS. If you don’t mind staying on the legacy platform the $$/SQ is tough to beat.
how can you use qobuz with ndx? just for my curiosity
The mconnect upnp app on my iPad let’s me play Qobuz on my NDX.
I have a bluesound node 2i connected with naim dc1 to nds and use it as reader of anything I want to try, from apple music to amazon to qobuz, I pretty enjoy it. you can connect an hard drive to its usb and indexes it in few minutes. nds in this case works as an incredible dac, still worth the choice.
I use a bubblesoft app running on my NAS that I control with the Qobuz (Linn) app and transcode to WAV for my 272. The SQ is sublime.
I used a NDX in my Olive system back in 2015 when I upgraded to a Classic system the first purchase was an XPSdr this made a very worth while upgrade to the NDX
I have been using a ND555 for several years but have had a couple of problem in the first instance ny dealer lent me a NDX2 and combined with a 555 ps I thought this was a stunning combination. On the second occasion I he installed a NDS this was the first time I had heard a NDS in my system and to be quite honest I was slightly disappointed with it.
I think you need to demo the options.
Yes, a demo would be a good idea. TBH I’m leaning towards an NDX2 - it appears that this should sound better than my NDX, and pretty close to the NDS, and - importantly - I can use Qobuz etc. with it if I decide to do that.