Buy a good hardware RAID card. Do not buy a software RAID card. Areca has a great unit and they are on eBay for about $100.

Fry's had 1.5 TB for $50 and 2 TB for $90 recently. Buy 2 or 3 or 4 depending on your budget, storage needs and whether you want data backup only or also increase in disk transfer rate.

Setup a RAID 5 or 6 or go nuts and setup a RAID 1+0 (don't go with RAID 0+1).

Sleep peacefully. You're as close to bullet proof as you are going to get at this level of expenditure. But just to be comfortable buy one more drive, copy everything to it and put it in your fireproof safe.