If your current version is 12.0.1.1019, and the installing version is 13.1.0.1058, I'm not sure why the OS would be flagging that as a downgrade.
Was the 12.0.1.1019 a custom driver from Asus, or the stock driver from Microsoft? If it was custom from Asus, you may have better luck with
http://dlcdnet.asus.com/pub/ASUS/mb/socket1150/P9D-E/Drivers/C22x_Intel_RAID_VER380110x.zip
from http://www.asus.com/Commercial_Servers_Workstations/P9DX/HelpDesk_Download/