word of warning:
ext USB hDD's are very unreliable.
the casing isn't unreliable
the hdd isn't unreliable
it's the USB technology with mass storage when it comes to ext hdd's that is unreliable.
I've had countless cases where the hdd's just fail to be detected.
i don't know how well firewire works or eSATA for that matter.
and for the HDD's - got with SATA drives. not IDE
on another story
when trying to fix my ext casing
one of the capacitors blew up about 1 foot away from my face