ok, in which way isn't the firewire-transferred video any good? The video you get through firewire is EXACTLY the same as is on the DV tape in your camera. A new GFX card ain't gonna fix that, sadly.
Is it still blocky? Is it the interlacing artifacts? What DV codec are you using to view the files? Go get yourself the panasonic one from
http://www.movie-codes.com and that should help you.