Recording commentary track for video clip

Question

I have recorded and edited some video clips and now i want to record an audio commentary to layer onto the audio of the video clip, like how directors do the alternate commentary track for a lot of dvds. It would be a recording of 2-6 people sitting viewing the video together with it's original audio.
Ideally,
1)I would mic each person and feed the mic into the computer to record them each as seperate tracks. I think stp can't do that, but garageband might?
2)I don't want the mics picking up the original audio of the scene they are watching, but I want the people giving the commentary to hear the original audio, as well as what they are saying and what the other people that are sitting in and recording are saying. So the only way I can see that working is to somehow have the original audio of the scene piped into headphones, along with the audio of all the other tracks being recorded.
So how is this all possible, either through my method or another method you could think of. And what equipment would i need, like a mixer or audio interface. If I can't do this natively in stp, than what can I use, like garageband, that i can import into stp for final mixing.

Answer 1

1) STP 1 can't do multi-track recording but STP 2 will be able to do it. In the meantime, yes, you can use GarageBand.
2) You're right, you'll need headphones.
If you want dedicated audio tracks for each one, you'll need an audio interface with multiple preamps like MOTU 8pre. You could also use only a stereo mic to record the whole room. That way, you could use an interface with only two mic pres and you'll need less mics too. And since it would be only one track, you'll be able to use STP. For this kind of recording, you'll want to use condenser mics.