here is a very thorough demo of the Casio WK7500. For the money this is an excellent keyboard. http://www.youtube.com/watch?v=ItTdzP_09ag

also i have afound a user demo that demonstrates the sounds briliantly. this is an awesome keyboard period . the price is just a bonus.http://www.youtube.com/watch?v=FFoODXzNjz0&feature=related

and this demo is just plain fabulous ! Korg need to emply this guy to demonstrate their instruments. Just imagine waht they could do !!

http://www.youtube.com/watch?v=mkozonnSfEY&NR=1

and here are the styles demos. A bit cheesey but its under £500

http://www.youtube.com/watch?v=AM3grHlPGEI&NR=1