@Mr. Tendo
You simply set both : intro-movie + startup sound
So you can do this:
1) Disable intro-movie or disable startup sound
start AM > press TAB button > Intro > Play Intro : No
start AM > press TAB button > Sound > press ENTER on 'Startup Sound' > move with cursor to blank line
2) with an external program (e.g.
audacity,
free studio and million other audio-programs) you have to add a silence to your startup sound:
for example, if your intro-video got ten seconds > set to your startup sound 10 seconds silence before