Standby after current song work only in player mode.
It doesn't work with aux.
(Nor with radio, if end of song is detectable)

End of song isn't detectable on radio. I can't see any way to reliably detect it. A period of silence doesn't mean the song's over... I would consider that a non-issue.

AUX is a little different but since I don't use the Empeg's AUX this one doesn't affect me.

I always have a player (cd or tape) connected to the empeg.
And this feature (-end of tune- detection) works realy fine!
At the end of my Queen tape (side 1), the last song is still right indexed (correct track#).
I think delayed standby can work with this mode (-end of tune-); and maybe -end of playlist- (end of tape in this case; e.g. 30" of silence).
In the case of radio, -end of tune- could be a mean to shut the empeg when the channel becomes silent (between 2 tunes, speaches, comments or st else...)