Hi,
if you're actually planning on getting a yamaha in the future, the fellow below has written a software version of an arranger keyboard.
Might give you something to play around with while you're saving up to get a new one.
There's actually a demo to download & try.
http://home.zonnet.nl/josmaas/onemanband/

It uses Yamaha styles which are freely available via the yahoo psr style group.

best wishes
Rikki