If you want to use the PERC card as a RAID5, do not use FreeNAS as the software. There are other software options but for what you want, FreeNAS is not what you should use, unless you don't mind your data disappearing one day. FreeNAS is designed to run using the ZFS software RAID and this also makes it portable, meaning that you can take your hard drives to any other piece of computer hardware, plug in the drives, and boot FreeNAS and have access to your data. You don't need a specific RAID card to get your data back.