Do you want to edit sound clips, or video clips? You mention below that you want to edit movie clips as well. Since this is the case, I would recommend something like FCE if you're concerned with syncing audio and video clips as you have indicated. Please clarify exactly what you need.
If you were just interested in audio editing apps, it sounds as though something simple such as Sound Studio would work fine for you - it allows you to do basic editing, cropping, and various effects as well, such as volume modification. If you need additional functionality, you'll have to look at more of a pro app...