Hey guys. Thanks much for the feedback. Re; @Embalmer, we've been able to use this voiceover process with no problem. It works quite well, but requires you to capture the video first, then do your narration/voice over. What we want to do is record the voice over while you were playing the game and recording. @Jim: the microphone is the way to go, but we can't get the new VideoWave software to record both the audio from the XBox feed and the audio from the voiceover. (This is what the "Stereo MIx" audio option used to let you do)
I think I found a workaround. We're recording the gameplay including the game's audio via VideoWave normally, and then simultaneously recording the voiceover via the PC microphone and the Windows Sound Recorder tool, which creates a seperate WAV file. We then create a Production and merge the gameplay video and the WAV file together to generate the final recording. Timing can be a little flaky but it seems to work.
Hopefully Roxio will allow the Stereo Mix audio option back in to the Recording feature, as they have with the Live Streaming feature.