I do think it is very inportant to check the capability of the firewire chipset on the mobo. It can be done by using a HDD conected on a enclosure with a tool such as hd tach. If the transfer rate for the HDD are higher than 23 mbs than , that speed can be acheeved with the dvd rw.

As my experience each and every mobo chips function not quite to standard
One more thing: I saw a simple connector for arround 12$ on thg (tom's hardware guide) test that can do the trick. The only thing u have to also provide the power either from the computer or from an external transformer from 220/110 to the power required by the drive

Sounds to me as a bargain