Part of the question you need to ask yourself is "why" are you going to an External HD?
Afterall, if it is for redundent backup, then two things manifest itself:
a) The backup should not be online all the time, since one power glitch can fry both original + backup.
b) Classical 'best practices' is to have 3 backup copies that you rotate through.
What I ended up doing was to go to an external HD with removable trays. One company that makes such a product is
coolgear, aka
cooldrives.
Basically, you buy one enclosure and then two additional HD sleds for it (total of 3 sleds), then go buy bare (internal) HD's and spend 10 minutes with a screwdriver to put the HD in the sled.
When I set mine up, I went with EIDE drives in the DK-9 enclosure, which has since been superceded by the
DK-12.
If I were to do it all over again today, I'd probably try to find something that uses a FW800/400 ports and removable SATA drives, so that I can recycle old SATA's into backup drives, or be able to build them into a
RAID 0, or whatever. Perhaps they have the perfect (for me) features combination, but I've not looked through their product pages lately.
-hh