SACD itch should be scratched!
Essentially, the difference is an obvious lower noise floor, most noticeable on material with space around the music.
How Quiet? Some, like a few of my Oscar Peterson SACDs are so quiet it seems like an un-natural quiet, but you may love that.
And, when not concentrating to hear the difference, it's not un-natural, just great artist and performance, I play the SACD.
....................................
Used: Lasers weaken, the 1st thing they do is stop finding the SACd layer. Have seller confirm it ALWAYS finds the SACD layer.
I found one highly recommended here (Sony xa5400es) with very low hours, sold by original purchaser (he had two, mine barely used).
I also checked, belts and the entire laser assembly is available to keep it going in the future
Now I don't see a great low use xa5400es for sale, but with patience one from original purchaser will pop up.