Did you compare these amplifiers in your own setup or at dealer?
There's something seriously wrong with the setup if you manage to get fatiguing sound out of those Naim setups. I've listened to SN2 + HiCapDR for three years now and heard 272 + 250.2 in several demos but not at home. Most pleasant sound with all the Naim strengths in all occasions. But at this level, if you feed poor signal to the amps or make poor choices with cabling, you can make them sound fatiguing. I've experienced this also so it's not impossible.
I use TeddyU2S to feed my Naim DAC and it does awesome job. Easily the best USB to S/PDIF converter I've used, and I've used many. Pure and clean sound with black background. Extracts much more detail than the Stello U3 which I previously used.
Hi Patu, in all fairness this was only auditioned at dealers location and not head to head in my home. Me and my brother who did the listening were equal surprised. It was a in dedicated hi treated listening room. Boths were on Naim Fraim support. Speaker were som Elac and they were boths run in so what made these setups sounds poor I can`t say.
Regards Magnus