easier to plug the two new drives into same RAID controller, make them a mirrored set and image the partition over using acronis or similar disk image app. Plus the small advantage of the image being written to the outer most fastest tracks.
...or disk image (acronis, etc. again) the drive across a network to another array/drive, then restore it back using the acronis bootable media. I do this often via gigabit LAN and acronis bootable media.
Getting the controller to write to dissimilar drives in an array may not be ideal, but might work with some controllers (assuming same partition size and similar performance mirroring can be more forgiving than RAID 0 or 5 with dissimilar drives and depends on controller used).. Let us know if it does work reliably and what hardware you used.
Stick with matrix 8.8 , avoid 8.9 for now...that's the thread I popped over from to share my 2 cents worth.