I have a Nait XS 2 amp which I have been very happy with for a couple of years or so, playing lossless Flac (cd rips) and hi-res files through my Oppo 105 and into Neat Motive SX1 floor standers.
I have been reasonably happy with the sound but know there is better available.
I bought an ND5 XS 2 streamer two weeks ago which has a non-performance affecting fault so it will be returned.
I am enjoying the sound more so than via my Oppo - I would describe the difference as possibly missing some small amount of detail but compensating by being a more ‘together’ sound. I can still follow individual music strands but find myself hearing tracks more as a whole rather than highlighted sections (surely what we are all striving for?).
Before changing my speakers I am convinced that there is more performance to be gained but at what cost? I consider myself to be very fortunate to be in the position to drop a few grand on improvements, maybe as much as £10K and then eventually half as much again for speakers (in the distant future). This pales into insignificance compared to some people but each of us are on a path and seeking to get the best possible for our respective budgets.
There are many conflicts or rather ‘differences of opinion’ in what the basic principles that need to be applied. These range from maximising the source quality even if current partnering equipment will not fully expose the benefits, to maximising the number of boxes with PSUs etc. Also, I am not hearing so much these days of minimising the length of signal paths - Naim would appear to advise bouncing the signal through as many boxes as possible!
My (not necessarily very scientific) research leads me to understand that the addition of power supplies certainly changes the sound and particularly for those fortunate to be able to afford the 500 series or even statement products. Whether these changes add to the musicality of the sound or reward the investor with more of ‘what they are looking for’ or indeed both, is down to individual preference/experience. One thimg for sure is that the law of diminishing returns in terms of performance gains versus price paid is prevalent.
I have considered the (differing) advise of several reputable Naim dealers, all of whom’s opinion I respect (ouch! apologies for the poor grammar!). It is apparent to me that the ‘Naim ecosystem’ would drain an awful lot of money and have people striving for improvement until they reached a full statement system! In no way do I mean this as a criticism rather that there are precautions required for us mere mortals with finite finances - it would be easy to get sucked into the ‘search for the holy grail’ and end up in a similar position to people with gambling debts if you had to seek finance for your project 
Thankfully Naim have a range of quality components for all but the most budget of requirements. I personally made the decision that I would limit the number of boxes pyrchased and then maximise my system within these confines.
The NDX 2 is the only choice as the 555 would require 2 boxes (and £20K!). Yes, it has display circuitry that I don’t need but it is the only way to get a better DAC than the ND5 XS 2.
For amplification the current best integrated (minimum number of boxes) is the SN2 - 10 watts more than my Nait XS 2 and several other improvements.
I have concluded that the two box system is best for me with the, benefit?!, that I could still add power supplies at a future date should I wish.
I may also consider trying a Chord Qutest or Hugo TT 2 DAC at some point in the future.
On to value for money, what do we get with Naim products? In my opinion all Naim products have a no nonsense family look that exudes quality and minimalism. I personally think that Naim looks fantastic - sealed boxes with no fans that do not run warm. Let’s not beat about the bush, Naim is expensive but you do get excellent engineering. Being designed and manufactured in the UK means that we are going to pay a premium but in my opinion it is worth it - R&D is not cheap and we all expect Naim to keep abreast of technology while maintaining the product integrity that we all like. It must be easy for them to consider cheaper foreign manufacture in a similar manner to a certain premium vacuum cleaner manufacturer that abandoned the workforce in Scotland.
Anyhow, back to the point, the RRP of my Naim system is nearly £8.5K and I am pretty sure that I could get great SQ for a lot less but I accept paying a premium to support a great UK company with great products (I am starting to sound like a Naim shareholder!).
I am listening to Hans Theesink’s album Bridges SACD rip while I write this and it sounds superb - it can only be better when I get the NDX 2 and SN2! Yes it is not the most demanding album for a system but Naim just makes it so musical. I equally enjoy far more complex/busy albums as well.
I am happy that I have made an informed decision, put down what to me is a considerable amount of money and am happy that I have been able to show constraint. I can’t wait to get the new NXD 2 and SN2, get it run in and then prove to myself that I have made the right decision - no pressure then!!
