20 year plus Naim user who has climbed the ranks with every pre/power until settling with the 552/500 15 years ago. Both units have just returned from a recap and DR and will be good for the next 15 years. Vinyl has always been a LP12 however my interest in digital started back in 2007 with my first demo of the newly introduced Linn Klimax DS. In 2011, after listening to both of Naim’s digital offerings, first the HDX and then the NDS, I made the move from CD to digital with the Linn Klimax DS/1. That was upgraded with the /2 and finally /3 until early this year when a change was made.
I demoed and purchased a Bartok which was to be used in a different room and for headphone only duties. Its performance so impressed me that I returned it to the dealer and moved to a Rossini + Rossini Master Clock. After 9 years the dCS has now replaced the Linn KDS in my Naim system which has now become 552/500 fronted by the Rossini and LP12.
I have many Naim friends who have gone with the ND555 digital front end when it was released last year. I have now been told there are many in the UK (I am in the States) who after a year have traded in their ND555 and moved onto the Rossini. My understanding is that all run full Naim systems however now with dCS front ends.
I have found there is complete synergy with the Rossini exhibiting quite a bit of good old Naim PRaT. I also agree with Pete that the Naim sound is fundamentally a NAC + NAP. The pre and amp together make the Naim magic. There has been a long thread on the forum echoing this opinion. The best quote was from the moderator Richard Dane who explained that NAC is Naim Amplifier Control. In other words one (the amp) requires the other (pre).
I know quite a few who happily run Naim pre’s into ATC active speakers, and I know quite a few who have tried to get by without using a Naim pre and have tried something like a Rossini directly into a NAP500. They have returned back to using the Naim pre. Ask Dunc on this forum who tried his Rossini direct into his 500 and was not happy with the results.
As to some of the alternatives you have mentioned I can only give you my personal opinion having owned a Nait 5, 282,252,552,250,300,500. The 252 was my least favorite pre. There are enough postings on the Naim forum to show that I am not alone in that opinion. The 300 amp is wonderful, and the 500 has made a quantum leap with the DR to become one of the best amps out there today. You will never find ANY complaints with the 552 which is universally loved, while the 282 imho is the great vfm in the pre lineup.
Of course a demo is key.
Good luck on your journey.