Nice system, you probably need a proper controller card to do RAID-5 properly, something around the ?200+ mark if you want to do it right. Cerro suggestion is good and is how my server system is composed, I boot off a raptor and have 4 disks in RAID-5 on a Broadcom BC4452 RAID controller for storage space... RAID-5 performs very well on a capable controller, but it has higher latency than a single raptor thusly the raptor is probably quicker at loading applications and things, whereas the array serves out files nice and fast.