umm, for audigy 2 zs i can use a little freeware called intelliremote (
www.melloware.com) but i don't know will it work with x-fi. With this program, my audigy2 remote (model RM-1500) can be used and configured just like media button (play, pause, stop, next,etc) on logitech keyboard. BTW, you'll also need microsoft intellitype pro software from microsoft site (no, u don't need to have the microsoft keyboard, it'll work just fine with any keyboard, but i don't know if it'll cause problem with your logitech keyboard software) for this program to work.
cheers.