When I listened to both the keyboards I used the internal speaker system.
I both played the same melody on both machines with the same voices.
I tried several voices, like the flute, trumpet, piano, saxes etc.
And I found that the Ketron's voices were more natural and realistic.
Later, I've listened to the PSR2000 thru some high quality headphones.
(I didn't have the chance to listen to the Ketron with the headphones)
It sounded a little better, but still not near as good as the Ketron XD9.
I also found the styles of the XD9 much better and more realistic.
When I was playing the PSR2000, it felt like I was playing a keyboard, When I played the Ketron, It felt more like a real band playing along.
I also tried the Tyros and played the same voices, the piano was much better, but the sweet voices sounded pretty much the same (they had the Yamaha TRS-MS01 connected to it).
When I asked the store owner what he thought about the Yamaha and Ketron he replied: "The difference between the PSR2000 and XD9 is the same as Black&White and Color".
Hope this helped.
Greetz
,
Marcel