Bill, I mean no disrespect and I do mean that, but do you even know what Magic Lantern does? It doesnt sound like you do because you mention that the AGC is always on which it is NOT with the Magic Lantern because this Firmware disables the AGC.
ML also added audio meters and turns the 5D Av jack into a headphone jack in addition to many non audio related features. Did you know any of this? Again, no disrespect but it just sounds like you answered this thread without knowing what was being asked.
A JuiceLinked unit in conjunction with ML drops the Audio input noise seemingly to 0.
Magic Lantern is a free 3rd party Firmware for the 5D not a Canon written product.
We all know that there are several ways of getting “Lucas” quality sound out there, but the question here is, does anyone out there have a lot of experince with both the options mentioned above and how do they perform?