Izotope Ozone 4 kicks arse!
In case you are not familiar with Izotope Ozone it's a mastering processing suite made by Izotope. As I just stated, it's made for mastering, but I use it all the time on an insert on channels when I'm mixing. This app is so sweet and for only $250, in my opinion, it's a steal. You can read all about it and download a fully functioning demo from Izotope.com.