Ok, audio is working fine in general now, I do noticed some problems, though. I can live with them right now, but they're still annoying: After a longer period of sleep (if the mac sleeps for more than 15 minutes), sound does not come back after sleep. If I change the volume to a very loud setting, the sound is playing, but it's only a distorted and crackling sound, that is only recognizable as music because it has a repeating rythm to it. Sometimes it helps to switch the audio cable from the back audio port to the front port (sound comes completely back then) but sometimes that doesn't help and I have to reboot to get audio back. If I boot with the audio cable in the front port, only the front port will works, if use the back port initially and the problem arises, I am sometimes able to fix it by switching ports.
Also, when no sound has been played for a while (about 3 minutes) (when the sound is idling, so to say) a repeating cracking sound appears. Every 2 seconds i can hear a crack lasting for about half a second, until I play some kind of sound to get audio back from idling, then the cracking stops for 3 minutes, but when I don't play any sound again, the cracking comes back after 3 minutes when the sound is idling again.
Any idea what's causing both of this? As I said, I can totally live with it for the time being, but it would be cool to have that problem erased, too. My config hasn't change since my last posts.