Which cable should I get? What length? Why bother?
Use your existing FireWire 400 cables with this FireWire adapter from Sonnet to connect FireWire 400 devices to a FireWire 800 port, without going through the trouble of purchasing yet another cable. Just plug it in between a FireWire 800 port and a standard FireWire 400 cable's 6-pin male connector (the other end of the FW400 cable plugs into your FireWire device). It can't get any simpler.