Rennie, I would get the speed rather than the storage. Hard drives are the biggest bottle neck on data these days. Processors and ram are speedy but the HDs really haven’t changed that much in the last few years. If you can get definitely stay away from 4200. It is painful. I know from experience.
I think that Ambrosia’s SnapsProX would let you record the website in a Quicktime video and then you could use any number of programs to place it in the video.
I was working on the same type of thing and I did this and it worked just fine. It’s kind of backwards to do it this way but if you are in a pinch this works well.