The big one and there's not much else to say: whoever has heard music through a pair of these Class A monoblocks knows what I'm talking about.
Granted, finding and listening to Sony's ultra gear is difficult... for that brand is known to have not marketed most of its ultra units :
whether its ESPRIT series, its monster LaserDisc players, its R1 and R10 series or the "1" follow-ups.
A distribution often restricted to Japan's domestic market, no reviews, no worldwide drooling and, hence, Sony after all only makes great portable gadgets :-(
However, the TA-NR1 is fairly easy to find because it sold rather well - Sony makes excellent High-End units.
The NR1 was withdrawn from the catalogs fairly quickly everywhere but remained available in Japan until circa 2000/2001, on special order, just like the fully MOS-FET and bigger TA-NR10.