The Rogue Amoeba application that you'd want for this is Fission, which is for editing--Audio Hijack is for recording. Both are cheap, simple, and good. Garage Band offers a lot of options, which can get in the way of each other when you want to do one specific thing. With Fission, you can just drag and drop your sound file to the icon, and it will open, and you can cut and paste without fooling with anything else--Audacity is very similar--