The Windows Experience Index is a total waste of time and it doesn't matter if you run a RAID0 on it you won't get a score of more than 5.9 whilst using magnetic drives. You will have to move up to SSDs for any better scores. It's just a joke really.
You might find that the drives would perform a little better in AHCI mode but you definitely have htem on the faster ports now. If you want to do this then follow these instructions:
1.Exit all Windows-based programs.
2.Click Start, type regedit in the Start Search box, and then press ENTER.
3.If you receive the User Account Control dialog box, click Continue.
4.Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINESystemCurrentControlSetServicesMsahci
5.In the right pane, right-click Start in the Name column, and then click Modify.
6.In the Value data box, type 0, and then click OK.
7.On the File menu, click Exit to close Registry Editor.
After this you’ll have to restart your computer, go to BIOS and enable AHCI. When you log in to Windows again, you’ll notice the installation of drivers for AHCI. Another restart will be required to finish the driver installation.