Get the triton TR (get the sampling board and max the RAM).
That'll beat both 500 and 900, and still cheaper.
you'll have aftertouch,on board knobs,APGTR,tons of sounds and 3 rd party support and so on.
or put a little money and get the Triton Extreme.Still around $1600 , pay 100 for full Sample RAM, and you'll have the best in the market for Electronica(yes better than Motif ES and Fantom X -IMO).
[This message has been edited by jamman (edited 03-29-2008).]