Here is something you can try before you buy:
http://www.home.zonnet.nl/JosMaas/onemanband/index.htm
It is a shareware program that makes it possible to load styles from your PC harddisk. In fact it takes over the task of the arranger part of your keyboard, so it can be used on keyboards of any make. But it is mostly used by owners of Yamaha PSR's that don't have a hard disk.

Jos