No digibeta deck that I know of has a firewire port. Better option? Meaning what? Cheaper? Better quality?
Have you checked the delivery requirements for Discovery? What do they want? My guess is a digibeta master, not DVCPRO 50.
So, either you're dubbing your master (not a good idea) or you should buy an AJA box/card or blackmagic card to do a proper output. The cost of thoses cards is approximately the cost of a bunch of dubs.
Good luck.
Mark