For my part, I think a lot depends on what kind of music you prefer to do. Modern WS's excel at complex electronic sounds, etc., but their emphasis isn't always geared towards acoustic sounds. Many arrangers, IMO have some acoustic sounds that are FAR better than some of the top WS's. Your S910's SA sounds are hard to beat (if played well) by most WS's, even including the MoXS, which has a derivation of the SA spec originally invented FOR arranger players.

But heed chas carefully, in his advice. He has hit the nail on the head. From your demo, it's clear you have quite a way to go before the basic sound is going to matter very much...

Walk first, run later.