I'm building a server with a RAID5 array, based on a hardware controller. I want to be able to later add additional disks and have the array rebalance across all of the disks, enlarging the usable size. I also want to be able to later upgrade to bigger disks (one at a time, of course) and then expand the array to fill the entire drive.

These features are available in Linux software raid (md). I've also heard they're available in some hardware controllers. Currently, I own the Adaptec RAID 3805 card and the 3ware 9650se card. I'd prefer to use the Adaptec if possible, but I can't find if either of these cards offer this feature.

If they don't, are there other affordable (read as: sub-$600) RAID cards available that can accomplish this?