like most things you can get branded and unbranded goods. the likes of belkin and others will be expensive, while the Chinese clones of these will do the job just as good but be cheaper.
also consider that firewire cards come in different flavours. You can have the 1394a which is a max of 400Mbps or the 1394b which has a max transfer rate of 800mbps. b cards or a mixture of a + b will be more expensive than straight a standard cards.
have you a link to the cards you are considering?