If I am using (4) or fewer hard drives, should I use the onboard firmware controller or an add-in hardware controller card?
The onboard firmware controller can support up to (4) SATA hard drives (as well as 2 IDE hard drives without RAID), however, it only offers RAID functionality under Windows, and it does not support RAID 5. If you use a different operating system, or require RAID 5, you will need a add-in hard drive controller.