C: Samsung 840 Pro 256gb SSD for OS & programs & pagefile
D: Samsung 840 Pro 256gb SSD for media cache
Samsung Spinpoint HDD 1TB Add to the raid5 below
E: Samsung Spinpoint HDD 2TB for projects
F: Seagate 1TB HDD for exports and previews
G: Raid5 (5X Samsung Spinpoint 1TB HDD on a Highpoint RocketRaid controller card) for media
Use additional disks for backup purposes.
I know that disagreeing with Harm is usually a silly and irresponsible thing to do, but this time I might suggest that the 5th 1TB Spinpoint that he suggested that you add to the RAID might prove handy off by itself for use as a place to store resources that are useful for multiple projects or that are unrelated to video editing.
I have such a drive for my Windows 7 "My Documents" folder. It comes in handy in that it is backed up at a different rate and in a different way than the other drives (Internet based backup instead of local drives).
Just a thought.
Steve, I mainly suggested a 5 disk raid5 for some security, especially for media. In speed it will be almost as fast as 4 disks in raid0, but now you can encounter a failed disk without losing data. And the OP has sufficient other disks.