I would go for the SD1.
I have played on the Ketron XD9 (The XD9 is the SD1's little brother, it sounds the same and it has a lot of styles from the SD1), And I was really impressed by its sounds & styles.
I've also played on a Yamaha PSR-2000, The PSR-2000 is a nice keyboard, but I think the XD9 sounds much better.

If you want some more demos, here's a link: http://www.mira-multimedia.de/KetronHotline/xd9demo/xd9demo.htm

These demos where taken from the XD9, not the SD1, but the SD1 sounds pretty much the same.

Good luck!!!

Greetz,
Marcel