I feel like I once had a PrefPane for this problem but just am having a hard time searching for it. Currently I have my heaphones jack Line-In routed to my AV Receiver for iTunes music in my room, but whenever I am YouTubing or other stuff while listening to music the System Sounds come out of my Loudspeakers too. I am interested in routing only the iTunes audio through the headphone jack, and everything else to run through my iMac's internal speakers (2007 iMac AL). Any help on this? I saw the SoundFlower thing out there but didn't think that was the ticket. Any help?