recording garageband audio and QuickTime/Imovie video simultaneously

Hi. I am trying to record video and audio simultaneously using my macbook's on board video camera and GarageBand using an apogee duet 2 audio interface.

Fortunately, QuickTime, Photo Booth and IMovie programs all recognize my duet 2 audio interface which is connected to two contender microphones for vocal and guitar.

Unfortunately, the signal is completely dry. It sounds great through my headphones when I have GarageBand running in the background with reverb and compression but bone dry when captured through any of the above mentioned on board video recording apps.

Any way of getting QuickTime, iMovie or photo booth to hear the reverb and effects of GarageBand audio short of detaching audio in iMovie and adding the GarageBand track separately and synching them?

That sounds very tedious to do that for every song I'd like to post.

Or, are there any decent sounding iMovie plug ins to add a touch of reverb and or compression?

Or third party software? Anything that can accomplish this and simplify the process would be great.

The audio effects built in to iMovie sound terrible compared with GarageBand.

Please help!

Thanks