Amplify mic even more Is there a way to amplify the input audio even more then how far the slider goes on system preferences? 

Maybe an application or something?

I am using line-in to pass a small signal through from the mic input, and I can hear it ok when it is quiet, just it needs a bit more volume.
What kind of Microphone? Any pre-amplified microphone should be plenty loud (even too loud) when maxed. You may have to use a pre-amp of some sort, something like the ART PowerMIX III before plugging it into your computer.