Juiced Link makes an external preamp that gets around the AGC problem by injecting noise into one channel that forces the AGC circuit to its lowest setting, which in turn, more or less bypasses the on-board preamp. Then you can add clean gain using the external preamp. Cons are, however, that it's not for those on a budget ($400 just for the preamp) and that you lose one channel of audio.
http://www.juicedlink.com …-mixers-etc-c-66/jl-dt454
As mentioned before using an external audio recorder and syncing later is one of the more effective ways to get good audio with your DSLR. The options do scale with how big your budget is as well.
Thanks Joe, I know all that. I'm not going to waste the $400 on the silly JuicedLink box just to have 1 channel of audio. I have a DR-100 recorder as well as about $40K in audio recording gear, mics, wireless sytems, boom poles and enough cables to choke out a horse. I do audio for a living and have worked with the juicedlink box on pro shoots in the past.
I'm just **** here. But your info is true and spot on. Thanks! 



