Most of us like to upgrade when we feel the need and when the benefit of doing so has been properly appraised. This usually means upgrading in steps unless you have the financial means to go straight to the end game, which I would suggest few of us have. It is also human nature to 'test the water' before we dive in.
Like so many, I have upgraded in steps (possibly a couple too many steps, I grant you) and have been appreciative that Naim have a sensible ladder you can ascend and it is your decision of how steep the ladder is set and how quickly you wish to ascend. For example I happily used my NDX bare for quite sometime and loved the uplift in SQ a separate streamer gave me. I then added an XPS (of sorts) and and then a NDS which gave yet another huge uplift in SQ. Finally a 555DR was added to the NDS which, quite frankly, took the NDS to another level again.
I realise that a ladder with so many rungs can be confusing and at times creates some redundancy, but I applaud such an approach as it allows the music lover to progress in small or large steps, according to desire and affordability.
Personally, I don't thing Naim should alter their upgrade and audio philosophy. They clearly believe separate, linear power supplies using well specified transformers is the route to optimal SQ. Having heard what an upgrade to a power supply does (on both sources and pre amps and indeed power amps with the introduction of DRs), I can only concur with Naim's philosophy here. The importance of the power supply also explains why Naim have invested so much in introducing DRs wherever they are effective. And I applaud Naim for making the addition of DRs an upgrade we can all choose to have done on our existing power supplies.
What is not to like, assuming box count is of less importance to you. If you can only accept a low box count then there are other wonderful audio equipment manufacturers that can oblige, but it simply is not part of Naim's DNA.