It would be nice to test:
1) RAID 5 with 12* SAS 15K
2) RAID 5 with 12* SAS 15K +1 * INTEL X25-M SATA SSD 120GB (with Cache Cade software)

this would allow one to measure the boost of a Cache Cade solution.

On a Cache Cade - I believe that this is feature of a firmware and it's OS agnostic - it's LSI card that decides which data goes where (hot - SSD, cold - HDD). So as long as your OS has got driver for particular a card you should be fine.