How to route two audio sources simultaneously as inputs to Skype

Well, seems like I just had to think about it a little bit more. My workaround is not possible using only system utilities. I used Soundflower and LineIn from Rogue Amoeba software.

Using LineIn, I could select channels 3-4 specifically from the PreSonus device and route those to the two-channel Soundflower device. Then, I simply selected the Soundflower device as my input in iChat.

Turns out I had some strange Core Audio driver issue. Every time Skype was running, process "coreaudiod" would fire up and begin to hog CPU like crazy. I fixed permissions on my boot volume and it fixed a bunch of stuff related to iTunes, which apparently also fixed whatever was going on.

Once the coreaudiod issue was resolved, here's the setup that is working perfectly:

1. Skype "microphone" (input) set to Soundflower (2ch)
2. Aggregate Device created, consisting of Built-In Microphone and Soundflower (2 ch.)
3. Reason set to use the Aggregate Device
4. SoundflowerBed set to output to Balance.

Now all I have to do is create an audio track and enable monitoring, and I can hear myself in the mic, while normal Reason audio flows out both to Skype and my Balance to my headphones, and all is well with the world.