even RAID with 1 or 2 disk failure is not a surefire secure backup method. as the whole RAID itself can fail and take everything with it.
RAID will not be cheap, at least $300 for a decent enclosure, plus disks
RAID will get you speed, and some insulation from disk failure.
it also gives you larger volumes, so if you go past 2TB of movies, you don't have to split them between disks.
for basic movie watching, the speeds you can get from RAID are overkill. Even straight Blu-ray Rips are under 4 MB/s, USB2 easily handles 20-30.
faster is not always better, you need to look at your usage, and pick a solution that works for you.
depending on how important the files are to you, absolute best backup solution is an offline backup at your location (something you plug in once a week or so to make current, then unplug and put it in a safe place). And you'd have a second backup disk that you keep at your office (or a friend's house) and once a month swap the 2 backups, meaning even if you loose your house, at most you only lost a month of data.
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also ...
time machine backups aren't the most stable things, they can corrupt themselves pretty easily, it's a good to have for an "oopsie backup", but don't depend on them 100%. (as i've learned the hard way)
