B & W 801 Series II Vs Yamaha NS 2000

In my opinion the B&W 801 series II is a much better speaker, but the Yamaha NS1000 is a better match with your amplifier.

I agree with Rrog. If you are set on keeping the Sansui, then the Yamaha is a better match. You would need more amp power to drive the 801's.

The 801's are very power hungry. You will not get what this speaker has to offer unless it is mated to a high current ss amp. I was running a pair with a Bryston 4B (250w) and the sound was ok, but when I added another 4B and ran them as monoblocks into the 801's did the music really shine. They also need to be on a good stand, in a big enough room to open up and are fussy with placement. Taken all that into account, they are big and bold with a non fatiguing presentation when mated with a tube preamp.
I don't have any experiencer with the Yamaha speaker.