I own the PSR 740, and I'm very very happy with it. When I found out that the PSR 8000 only had two variations and fill ins per style, I completely lost interest in it. I really appreciate having four variations per style. I really like the styles on the PSR 740 and how they build up subtly from start to finish without ever becoming too busy. With four fill ins and four variations, you can really bring life to a song and the styles remain fresh to one's ears much longer. I find when listening to styles from the X1 or Korg styles converted, the styles are so built up that there is really nothing to do with the right hand without sounding a bit cacophonous.
I would go with the PSR 740 or the 2000, if you can afford it instead of with a used PSR 8000. I would only choose the 8000 instead of these keyboards if you're into a lot of midi playback during a performance, because the PSR 8000 has the hard drive and some well praised midi playback features.
Just my opinion.
Larry