Check out
Check out WiebeTech.com - they have lots of stuff for firewire RAID.
My two cents:
I had an external - and took it out and put it inside my G4 - way happier. But alas, you can't do that (I have a new AuBook too - so I've been thinking about this).
A thought if you do ALOT of video, get a FireWire 800 PC Card and connect it that way, YOU SHOULD SEE A SIGNIFICANT difference.