I need to populate the bays of my new MacPro 2.66 with 5GB RAM. The stock HD turns out to be a Seagate 250GB HD ST3250820A. I've found them online and wonder if I just should RAID three or four of them as opposed to one Seagate 500GBs or 750 with 32GB cache? These would all be a Raid run by Apple software not a RAID card. My use would be with Adobe Lightroom and some light video work. I do have 1TB of external storage.