[ChuckS]

I don't have answers to specific video recording equipment, but one thing to keep in mind is that audio inputs of video recorders often go through automatic gain control (AGC) located within the video recorder, which is typically not good. Also, if you're using an analog signal from your portable recorder to the video recorder you are not taking advantage of the audio recorders analog to digital converters (ADC), and the ADC in the video recorder is probably not as good.

Something you could consider is recording the audio separately from the video (audio and video recorded on separate devices but at the same time). This will take full advantage of the audio recorders electronics. You would then need to combine the audio and video files.