For a while I had a PSR8000, 9000 and 740 at the same time. Listening to recordings of live performances, you couldn't tell the difference except for the unique sounds that one or the other had.
Actually the 8000 seemed to have a "smoother" overall sound, probably because of e.q.
I found that the 2000 and 2100 sound better out of the box than the 9000. In other words less editing and "tweaking" required.
I still maintain that some of the Tyros sounds and particularly the drums are quite a bet better than all the Yamaha predecessors.
DonM