what I did on my ax-4000 was this:

all my devices go through my a/v receiver so that is the only volume I have.. actually my tv volume is disabled through its menu.

after setting up all my devices and xpress functions on the rm-ax4000 I went back to each device screen and changed the volume button by editing its function and choosing the alias for stereo volume up, down and mute.. and then saved the device again.. this will and does work..

Derrick