PE860 SATA RAID question

Just trying to configure a PE860 server for work and have a question regarding the SATA RAID confuguration.

We want 2x 160Gb SATA drives for a RAID1 Mirrored disk config. Would we need the optional SAS/SATA internal RAID card to get this config ??

I see this server has an onboard SATA controller. Does this do RAID 1 Mirror ?? If so, would there be any benefit of using the SAS/SATA internal RAID card over the onbaord solution.