Download the free 10day trial of this
http://www.izotope.com/products/audio/nectar/ and have a good play around. You can use it as an AU inside of GB.
Also, it might pay to do some research into external soundcards with good A/D converters. I love my Rode NT2000 condenser mic, but it was beast to tame.
Room can be THE biggest culprit. L.ust has good advice ^^^.
There are some room correction systems out their too.