Late to the party guys,
Now I am somewhat biased as Art mentioned because I am building these amps up and think they are awesome, but what lead me here was that I personally tried a LOT of different amps prior to the nCore (mix of Valve, Class A vintage, A/B older and current plus various Class D + Commercial Class H variants) and was always missing something... and then over the last year I found something I really liked and decided to compare as many amps as I could directly against the nCore and in the case of this thread, I specifically had a primare i22 for 2 years as my office system amp. So I got to do some extended A/B/C testing between that and NC500 & NC1200 with IC opamps and then with custom buffer boards and a range of different opamps.
I didnt stop there, I have also tried near a dozen different speaker setups aswell to get a good cross section and idea of what the amps are capable of. Drop me a line if you want to know more.
In the end I sold the primare on here to a fellow member in favour of an NC500 for my office system and spend 90% of the time running the Sparkos 2590 opamps for the office system which is tannoy 6.5" dual concentric inwalls with supertweeter (IW62 TDC) + passive tannoy sub (IW62 TS running 1 driver per channel for a 4ohm static load). Dont let the inwall fool you or size, these are very accurate and capable speakers that can handle serious power and are very revealing of equipment in the chain and recordings/formats.
The primare was a very nice amp and I was really impressed and happy with it until I heard the NC500 running the same setup and it was a definite improvement for me. In terms of bottom end punch and control, the only amp I have had better this is an NC1200, but this is quite excessive for this setup IMO. Mids are crystal clear, bit I did find the top a bit dry and shrill at times with the IC opamps - most obvious with high ranging female vocals (London Grammar, Adele, Sia etc) and some wind instruments.
The warmest of all opamps I have tried so far are the Sparkos 3602 and closely followed by the SIL 995 FET and these seemed to tone down those top end frequencies quite nicely for my setup, but I think the 2590 is a better all rounder considering how many hours I spend listening to this system a day (far more than the main hifi setup, theatre or car systems combined!).
Now I am in the process of doing up a Purifi 400A to pitt against the NC500 with same PSU/Custom Buffer Board and range of Opamps and will let you know my thoughts in the coming weeks once I have spent some quality listening time with them. I will also compare it to the NC1200 aswell in same buffer/opamp combos to be thorough.