You can also look at the T-racks suite from IK Multimedia. They run sales all the time. I have both T-racks and Ozone. I prefer Ozone but T-racks has a nice RMS meter that will measure the perceived volume. It's also a great way of seeing how compressors and limiters effect the volume along with letting you see the frequency spectrum and stereo spread of your mix. I have found it to be very useful in identifying problem low frequencies.

You don't need both. Each has a set of mastering plug in chains that will do the job you need. T-racks also uses some emulated vintage compressors which can give some nice coloration to your mix.