I haven't tried Audition yet, but I use it's predecessor, Cool Edit, to remove camera whine - the Noise Reduction facility. Marc, with your quality of camera this may not be a problem for you anyway.
I use Soundforge for looping and editing music and voice overs. You can normalise, add echo or reverb etc, I daresay Audition will do all that too.
I use Acid Express to build pretend ambient tracks, birds, water, any other relevant sound effects, if Audition will multi track, you could use it for that as well.
Win XP, Athlon 1.8, G force 3 T, 1 60gig drive + 1 250 gig, Pinnacle Studio 9 plus mostly, Premiere 6, and Vegas 5 sometimes, Soundforge, Cool Edit.