Thought they both did.
Maybe not.
I use the gs500 mainly, so i can only comment on that, but they were all part of the same product line, so chances are their audio circuitry is similar or the same.
I always run the headphone out on my DAT into the mic in on the DV cam, the result is always excellent.
While the 500 does have gain control (assuming the 320/300 does too), even to it's lowest setting, if youre taping loud gigs, youre prob going to need something in between the mics to help your signal down a bit so it dosen't distort.
That being said, you have everything setup properly, the panasonic 3ccd dv cams will give you some of the best audio and video of standard definition dv cams in concert settings.