Is it possible to transfer both Voices and Multis from a Motif XS rack to a motif XS8, and how?

Yes it is possible - there are two methods: one for if you have both units in the same place, the other for if you have to transfer data when they are not near each other.

1) MIDI Cable from MIDI OUT of the Rack XS to MIDI IN of the Motif XS8
2) Use the computer Editors. "Yamaha Motif-Rack XS Editor Standalone/VST" and "Yamaha Motif XS Editor Standalone/VST"

The Editors are available from the official Yamaha download site: http://download.yamaha.com

Great! Thanks B_M