You should give this one a go if you haven't already (and are OSX based). It can really boost a poor quality recording (in fact it's pretty amazing if you ask me) though I'm being more and more tempted to switch it on for good quality recordings too as it can give anything a little lift. I guess it is just like an equalizer on old amps except you can mess with the soundstage and clarity, though I do feel a little guilty when using it.
Try it see what you think, it's cheap and won't disappoint.