Real Time Spectrum Analyzer?, Real time spectrum analyzer? Options

[unitypunk]

Hello everyone,
I f anyone has a suggestion in this matter it would be greatly appreciated: I'm running Reason 3.0 on a Mac, with a PreSonus Firebox as my audio interface. I have Cubase SE for some post editing, but usually don't use it nowadays unless I am recording vocals or instruments. My question is this: is there a real time audio spectrum analyzer for the Mac? I'm looking for software that I can use with my current setup so that I can visually analyze what is playing on Reason (in realtime, not as an exported audio file), and tweak the audio within Reason before exporting the file for later editing. All the software and VST demos I have downloaded and tried out don't register the audio coming directly from Reason, regardless of how I set up the I/O in the preferences.
Again, any suggestions in this matter are greatly appreciated.
Thank you