I have an Areca 1880ix-12 RAID card in my 4,1 --> 5,1 Mac Pro, and it works great with 4TB HDDs, for the record.
Of course, it also can use up to 4GB of cache memory, does other levels of RAID such as 3, 5, 6, 30, 50, 60, and it's a much faster x8 lane card that can handle 16 disks for about the same price as the Apple Pro RAID card... but that's another story.