Two things:
Definitely agree with Indy on the hot spare. It's like allowing you to have more than one bad drive.
Second: I may be looking at this wrong, but from the list of HDDs, it sounds like you don't have a drive yet. I would recommend having the HDD on premises so you can swap it out immediately. Otherwise, your running slow and hoping no drive crashes while you wait.
I would also go with the Enterprise drive.
