The voices on the S900 should in principle be capable, but like many they can (and often need to be!) improved upon.
Even the modest non-SA sweet violin can be improved to give a more gutsy performance, to the extent of bringing out articulations you may not have guessed were there, just listening to the preset voice.
I've uploaded a zip file containing tweaked sweet violin, SA Trumpet and 2x SA saxes so you can try these and see what you think. (Download and copy to USB. Then with stick in the S900, push any voice button, navigate to the file and select it to load into R1 or 2).
http://www.box.net/shared/z7zq4o49vi

Three of these were made on Ty2 so should be compatible with the S900. The one I'm not so sure about is the SA RockSax because I have made mods and resaved it on Ty3 but on the face of it, it is still a similar format file & should also work. I included the latter since it is a slightly stronger sound than the BigBand Sax. Try both saxes and trumpet with harmony switched on too - to assess the quality as ensembles.

John