I'm 99% sure that only the first 2 channels will be imported. I've seen some weirdness where multichannel audio has been bounced to a stereo pair on import causing a jump in levels. Your best bet is to use Soundbooth (or Premiere) or an audio/editing app to do the conversion.
By the way, what does "audio has been bounced" mean?
bounce = shifted/remapped to another track