if you are to buy either one of those interfaces all they do is transfer the digital signal from the d8b to the DAW. I would go with 9652 it will be faster than the firewire unit and plus it's RME so its reliability is unquestionable in my opinion.
The d8b is essentially your analog to digital converter. I suggest downloading the manual and reading through it to understand how the hook up of mics and such relate to what your wanting to do.
-Casey