The high end Sansui products from the late '70s were excellent. That being said, Sansui had a lot of variation in quality through their extensive product line, so don't just go out and buy the next vintage sansui you find. If you find the right one though, you can have a really great amp.
That pretty much goes for any brand in the 70's 80's. You really need to be picky and know your stuff here, for every gem there were 50 pos's made.