Stick with hard drives.

Seriously. Unless you need the portability that optical discs offer, just use hard drives. It sounds like you've spent quite a bit on disc space already. You could build a 6 TB RAID 5 array with cheap SATA drives (5 1.5 TB drives in the array). That would give you all kinds of space and some redundancy. And if you want to back that up (which I do recommend), you can get 4 1.5 TB USB drives. Back the whole thing up to the 4 drives and you're all set.

Do you really need all that stuff though? Are you ever going to find time to watch it all? I'm thinking the same thing as C3PX. What good does it do to have all that stuff if you never get to watch it? Do you have parties a lot where you just want to be able to watch whatever you want, whenever you want?

Anyway, the hard drives are probably far more likely to last then the optical media is. Recordable CDs and DVDs are notorious for failing after a few years, so you really are better off having everything in an array on the hard drives.