Hi, first of all, Teamspeak is there for linux as well. Don't know if you have that version, but i can't make that up out of your story.
Second of all, to have multiple sound streams, it's my believe that then you need to have SoundCard that has Hardware mixing, which you can find @ www.alsa-project.org
If there's a 3 @ notes, it means your sound card is beeing supported in alsa WITH hardware mixing, this enables multiple sound streams.
I don't know if this goes for OSS too.