The simplest setup would be this:
2x SSDS in RAID 0 for pure speed (this will give you ONE logical drive in the OS @ 512GB) Store your OS, Games on this drive
You have 2 options for the other drives, but I would recommend RAID1 since you will already have a RAID0 with SSDs for performance: (Store large files, media, programs that dont need fast read/writes on this array).
2x 2TB in RAID 1 for mirroring. You will still only see one logical drive in the OS, and you will only be able to utilize 2TB, not all 4 since they are mirroring.
2x 2TB in RAID 0 for speed giving you a total a 4TB logical drive in the OS.
Always remember:
RAID0 will give you faster speed and more capacity, BUT IS NOT FAULT tolerant. If you lose a drive, you're screwed and have to rebuild.
RAID1 will give you more redundancy and less capacity, it is fault tolerant, as in if you lose one drive, you can still retrieve your data.
i7-3820 @ 5.0Ghz - RIVF - 32GB Kingston @1866 - Gigabyte Radeon 7970 x2 - Cosair Force GT 240GB x2 (RAID 0) - WD 2TB 7200 (RAID 1)