LetiMix

The best $19 you will ever spend on your mastering chain. I like this better than the $150 Perception plugin (which I also own). It's faster with a simpler intuitive UI. Further, this plugin offers groups and thus can be used throughout a mix session. It might even double as a vocal rider by putting the source plugin on a steady oscillator (with no output). Very cool plugin, giving me some interesting ideas beyond what it was made for. Don't forget to check under the hood; there is a ton of great tweaks behind the gear icon.