Hey Matt, you can really go to town with Saturn in terms of frames you collect and stack. Because it's so far away you can run long avi sequences without rotational smearing - I typically do at least 200 sec and get 2000 frames, but occasionally will join two together. I try and get 1000 frames for actual stacking and feel you need around 600 to really overcome grain issues. It's all a bit suck and see with each avi though so why don't you just set the quality for your to end up with around 600 frames and just see what happens - you might be pleasantly surprised... or it might be worse.
I'm in the dialup doldrums ao can't take your avi, but if you e-mail over a TIFF or BMP I'll see if I can tweak any extra out of it.
Cheers matee,