I think there is a mis understanding of what the DSP currently does in the Naim DACs and streamers... it’s not configurable, it’s designed as a specific low pass reconstruction filter for the DAC and matched with the analogue filter... its design is an inherent part of the Naim player and requires delicate optimisation in terms of execution timing.. having a configurable Naim reconstruction filter DSP is bit like seeing having a configurable DAC chip that be plug swapped out.
I think Naim looked at separate DSP sound optimisations, but felt the negative impact on SQ was not acceptable
With respect Simon (and unlike most times I say "with respect" to someone, this time I do actually mean it) I think you are missing the point.
There is no doubt at all that a significant number (most even, if the forum is typical) of Nova and Atom owners find the latest firmware update to be a big downwards step in enjoyability. Not all, but most. Some NDS owners are also not happy, but most are. I think all 272 owners are happy and there haven't been enough of the other streamer owners reporting to know what the overall view is on the old Unitis, NDX and 172.
It is at least arguable that Naim failed to find that point of delicate optimisation to which you refer, at least in the case of the new Unitis. In the case of NDS, perhaps there is no single point that could be found.
The Naim "golden ears" listening to their preferred material, probably quite loud, in Naim's room, using Naim's choice of speakers arrived at a conclusion which a significant number of owners find less engaging than before. We know from beta testing how much difference there can be between versions of firmware that are exactly the same except for the DSP coefficients.
The one thing you can be certain of is that none of their customers, not a single one, will have exactly the same ears, choice of music, room and speakers as the Naim reviewers. It may be that one DSP parameters choice is "correct", but if it sounds wrong to their customers, those customers will gradually leak away.
That's why Naim should offer a choice of DSP profiles and I'm sorry but it is total nonsense that doing so would necessarily damage SQ. if it is designed well, then it can be easily done.