Don't know about those, but I have a Nak 620 (circa 1977) and it sounds great and provides about 100w/ch into 8 ohms and 150w into 4 ohms. Interestingly enough, this amp operates in 'pure' class B with low feedback. With feedback removed, the Harmonic and Intermodulation Distortions are still less than .5%, according to tests done back 'when'.
The 600 series of products (pre-amp, tuner cassette decks) never did well in the marketplace, probably too odd. The 630 tuner-pre-amp jhad (has) a superb tuner section and phono.
Much of the reason for going with the 'Pass' circuitry was for marketing reasons, IMHO.
Salut, Bob P.