I don't have the keyboard with me or the data list, but there is one new Live! string voice on the PSR-S900, I think it's called Symphonic, but to tell the truth, it sounds the same as the other Live! strings. It might have a slightly slower attack.
You will not notice any improvement in string sounds over the PSR3000.
The differences I hear in sounds in the styles are with the Megavoice guitars - especially the nylon string guitar, and also just better mixing.
You will enjoy having a wide variety of quality trumpet, sax, and guitar voices to play with. Sometimers, I think I'm hitting the polyphany limit with some of these S.A. voices however. Sometimes when I choose a certain trumpet or sax combination, I get muted sounds like there is no more polyphany.
The OTSs are given more thought. They are mixed really well.
I don't think the keyboard is going to sound exactly like the Tyros 2 throughout all of the styles, because there are some Tyros 2 styles that when they are loaded into the PSR S900, the voices are missing or changed. The PSR S900 has less than half of the Megavoices and S.A. voices that the Tyros has.
BTW, the Music Finder is still pretty much the same in that you can't call up styles on the USB - just Preset and User styles.
I think the repertoire button has been mentioned. When you are in style display, for any preset or user style selected, you can press repertoire, and the Music Finder database will come up with whatever songs are suitable for that style. Good idea!f
Beakybird