I'm sorry if my post was not clear. I was not referring to NCORE impedance matching, as both the DIY NC400 and OEM NC1200 designs have all over 100K Ohms and don't present a challenge to the line stage devices.
I was talking about matching or pairing in terms of tonal balance, upstream. NCORE seems to be so neutral and with such an extended bandwidth, that it won't forgive not selecting the right source or line stage (by "right" I mean whatever makes you enjoy, feel the music you like).
NCORE, UcD as well as almost all the high end Class D developments were born, designed and optimized with professional audio performance objectives in mind. The first "audiophile" tuning has to be introduced by the OEM by designing the input stage (sometimes known as the brand sound), and finally completed by the user by choosing the right upstream components, also considering the speakers and room characteristics.
IMHO, it seems that NCORE, being so transparent, makes it a bit more challenging that final "user" tuning. However, if done correctly it can prove more rewarding.
The comment about the NAD M22 was just that, no intention to direct compare with the new Bel Canto amplifier, but in the general Class D and specific NCORE discussions it is worth to notice that it is not very simple to introduce an NCORE based amplifier in a playback chain and expect warranted satisfaction. I tried the M22 with a MacIntosh CD player and tube preamp, the speakers were Dynaudio Confidence C1 MK2. The result was a bit uninvolving, could not get the emotional connection with the music, only admire the resolution and dynamics of individual instruments.
Downstream, I read good experiences using NCORE with a wide range of sensitivities (even 104 dB horns) and impedance speakers, it does not seem to be a problem there.
I think the key to a successful NCORE based system is upstream. And these, as well as Anaview and Pascal, modules are so DSP friendly, that it is only a matter of time until advanced DSP is introduced into hardcore, purits, audiophile devices. French Trinnov and some other brands are leading this trend.
Cheers, Sebastian