Of course, your current configuration isn't using the RAM speed it was built for, so instead of getting the max 6.4GB/sec HTT bandwidth you are getting 5.4GB/sec max memory bandwidth...so you're basically looking at around 20% performance increase from that alone
You will notice overall improvements in RAM intensive games like HL2, BF2, and fear whenever it comes out, and any intensive rendering or editing will see a performance boost