Malachi

I agree with Don (he's too big to disagree with)!!
I owned a Yamaha PSR640 for a while which has a 32 note polyphony limit, the same as the Casio WK1800. This was THE main reason I upgraded to the PSR2000 which has double the polyphony. Playing some of the busier styles on these keyboards eats up much of the polyphony and you aren't left with much to play. I like to multitrack most of my songs and it was getting impossible on the 640.
You could try using styles without too many heavy strings or pad tracks, they seem to be the ones that use up the polyphony.

Will