I think I'll go with the usb external. I wasn't aware of the physical size restiction of the internal drive opening, thanks for the heads up on that. Also I read of heat issues using an internal for game storage.
i have a 750gb in my slim and its fine. and i don't think fw matters as to size acceptance, but if you want it for jb to hold many many games definitely go an external or 2.. much easier than running out of room.. LOL