When using the X1's FLASH card, the data is read directly from the card. It is NOT stored anywhere in the unit itself. RAM can only be accessed from either the HD/FD so, yes you will have to load the sounds.
Best way is to load them from HD on power up (such that whenever you turn on the keyboard, the sounds are automatically loaded). We cannot Load from FLASH to RAM as this will require a Hard ware modification.
These are good suggestions, however, they would require hardware routing modifications to the keyboard.