"650Mhz" DDR3 RAM doesn't exist. The lowest DDR3 goes is 800 (which is VERY rare). What you have now is 1333 RAM.
It's actually supposed to be 667Mhz, not 650, but it's close enough. 667x2 = 1333. DDR, remember. You're getting confused between rated speed, and actual speed. Not your fault, though. It's the stupid way that they're marketed.
1333Mhz would really be rated at DDR3 2666 (or more realistically, DDR3 2600).
On page 6, the reviewer wrote "The results weren't very stimulating, were they? Just as expected, gaming with faster memory just doesn't make any notable difference. I could have potentially lowered the resolution and settings in an attempt to produce some sort of difference, but I felt that testing these games at the settings they're most likely to be played at was far more enlightening. If you want better gaming performance, the GPU is the best component to upgrade—no news there."