Just to summarise (Kindly correct me if I am wrong)...There are mainly 4 volume levels...

1) Ringtone volume
Controlled by Settings--->Profile--->General
2) System volume (volume level used by media player etc)
Controlled by volume level in status applet.
3) Phone (non-speaker mode) volume
Controlled by volume keys when a call is made in non-speaker mode.
4) Phone (speaker) volume.
Controlled by volume keys when a call is made in speaker mode.

And all 4 are different ones and not related and like Traceur said above, the system remembers the volume settings for all the 4 volume levels.