I just purchased a new Mac Pro to replace my current Windows Desktop. I have 2x500 GB drives in RAID 1 now which I'm looking to migrate to the new Mac. Now, I need to expand my drive capacity so I'm buying two new drives to do a 4 drive RAID array. I really wanted to do a RAID 5 set but the Mac Pro RAID card is just too expensive (and it only supports 4x SATA drives) and 3rd party cards have gotten bad review. So instead, I'm looking at doing a RAID 10 set. To sort of future proof, I'm want to get 2x750GB drives but I have a couple of questions. First off, if one of the 500GB drives already has data, can I make the RAID array without having to reformat that drive? Second, I've never worked with RAID 0 stripes, so if I make a RAID 10 set (2x500 RAID 1 + 2x750 RAID 1, RAID 0 of both sets), will the max capacity be 1 TB or 1.25 TB? Finally, if later on I replace the 500GB drives with 750GB ones, can I update the set without a reformat?