Installed amd 965 125w black edition

For a start the Windows Experience Index means less that *** so ignore it. You will notice any increase in performance simply by using the computer.

It's likely though that the Index has dropped because Windows thinks you're running a slower processor than before. This will happen if you've not updated your motherboard's BIOS to work with the new chip.

Check if you motherboard works with the new chip and update your BIOS if required.

If using your system you actually notice it running faster then you're fine. If you notice it actually running slower then there's a problem.