This sounds good but leads to another option which would be a different solution for me:

When muted, pause playback and switch to the AUX input. I could then pipe the audio out of the nav into the AUX port of the empeg which would then automatically be a set fraction of the volume I was listening at.

I saw in another post that you can not mix AUX and player output without some serious modification which would have been my ideal solution.

MK2 Red S/n 949