The external case kits work just fine. I would probably go with either a combo case (has both USB and FW) or just USB 2 - make sure its backward compatible with USB 1 in case you want to use it with more than just your system.
. Check that it's compatible with all the OSes with which you might want to use it.
. I guess that there is some agreement that the Oxford interface chips are better than others, but it's been a while since I checked out that market.
. I don't think the pre-assembled ext hard drives are any better (as they are all built around the same handful of interface chipsets), but they for sure cost more... Check the user reviews on newegg. You have to take the positive reviews with a couple grains of salt, but the negative ones might help you avoid a loser.
.bh.
.bh.