Did you know there's a replacement for the S-500 that's set to release VERY soon.  
http://www.zzounds.com/item--YAMPSRS550  It's not much more than the S-500 and WAY less than the S-900.  
The S-550's features really stand out against the S-500.  Such as 64 note poly, 16 trk seq, and a style creator...  It's a good bargain compared to the S-500.
Just something you might want to consider if you're still within a reasonable return period for the S-500. 
[This message has been edited by squeak_D (edited 10-24-2008).]
 
_________________________
GEAR:  Yamaha MOXF-6, Casio MZX-500, Roland Juno-Di, M-Audio Venom, Roland RS-70, Yamaha PSR S700, M-Audio Axiom Pro-61 (Midi Controller).  SOFTWARE:  Mixcraft-7, PowerTracks Pro Audio 2013, Beat Thang Virtual, Dimension Le.