Hello Alec, the Orchestral 1 SR-JV80-02 is the board you should expand your XP's and the Orchestral 2 SR-JV80-17 is another good companion to the Orchestral 1 board. They have very good orchestral waves and programs for the oschestral and symphony style.
You will have most if not all the classical instrument sounds under your finger tips if you use a XP60 with both the Orchestral 1 and 2 expanded.

My 2 cents,

Keyman