You may need to consider adding another FireWire bus to your system. There are several affordable PCMCIA / PCI / PCI Expresss FireWire adapter cards that will do this, and allow you to use multiple bandwidth intensive FireWire devices simultaneously.
But please note: a port is not the same thing as a bus. Many computers / FireWire adapter cards have multiple FireWire ports which are SHARING the same single FireWire bus. Please check with the manufacturer to see if this is the case.