How to upgrade two raid 0 hard drives?

Hello, I have a desktop with 2x160GB drives in a RAID 0 array. I am trying to upgrade to 2x500GB drives and would like to keep the RAID 0 setup. I can't quite figure out how to go about cloning my system onto the two new drives. I am using Acronis from WD, and also have a Thermaltake Blac X Duet Sata drive docking station. I was successful at cloning my system to one of the drives, but the RAID 0 array was not active on them. I then configured them to RAID 0, lost the cloned data, and am back to square one. The two new 500GB drives are in the docking station. Under My Computer, I only see one, which I read can happen, but under the Device Manager it lists both of them. When I open Acronis to reclone, one drive is formatted, and the other is unallocated.
Can I ultimately do what I am trying to do using the external docking station, or do I need to plug my new drives directly into my mother board?
I have a Dell XPS 400.
Thanks.