An app for looking at sound levels for surround sound channels? I have been creating 5.1 surround sound files from Apple Compressor, but need a way to visually see that the different channels are all working properly in the final file. I can't test with a physical surround sound speaker set-up. 

Is there an app that can show the sound levels for each channel, like you can with mono/stereo files in Audacity?

I don't have access to a full video editor like Final Cut Pro, or Avid. I would happily pay for a smaller audio utility that lets you do this.
Try Soundtrack Pro from Final Cut Studio 2009. This is simple and robust application. There's surround 5.1 under its hood and moderate set of audio professional tools.