The Octopus cable is only needed if you plan to house your drives in an external chassis.
And honestly, I'd ask around here on the boards before I drop $100 on a cable.
As for your setup, yes, system specs. wise you are set. I would caution you though to get BIG HDDs! The VT doesn't save data in a compressed format so drive space disappears really, really fast!
And the HDDs you hook up to the Flyer cannot be accessed by the normal system either so plan accordingly....
For the green screen, I know that there is a video editing program for the Amiga that will actually take a snap shot of what ever background you are using and only record anything that is different from said snap shot. I saw a demo at a con and it was really cool. If I can remember it's name (or some one else jumps in and knows what I'm talking about) I'll let you know what it was called.
Other wise, I think there is a standard Green screen program built into the VT software. But that will actually require said green screen backdrop and no one on screen dressing up like a Leprechaun.
Total side note- I'm really into this old Xbox game called Steel Battalion and the giant robots in it are called Vertical Tanks, VTs for short. So I've been confusing my self through out this whole thread, getting distracted by all that!
PS- I know I'm sounding all pro about this, but I've never personally used them. We did sell, install and configure them out of our shop back in the day and as a Tech I got very close with all there workings.
GOOD LUCK!
