Whats the difference between cheap and high-end stuff?
The difference between the $ 750 packages and the $ 2,500 packages is mainly the existance of analogue inputs and independence of the package from the video camera. The cheap packages take advantage of the video camera circuitry for D/A converters; they don’t have to “reinvent the wheel”. The fancier packages have those converters built-in, so you don’t have to have a FireWire device continuously connected to them.