Either the RAM or the CPU will have to adjust itself to the other's settings.
In your case, the E6500 has a 1066 MHz FSB. That means 266 MHz x 4 (because the FSB is quad-pumped, don't ask me why). Now, your RAM is running at around 667 MHz (1333 effectively). Notice that if you multiply 266 by 5, you get 1333. There you go. That means your processor will work fine the way it is.
If ever you decide to overclock, I suggest you give attention to the CPU. The RAM gives virtually no increase in performance in games, and gives a negligible performance increase in video encoding/photoshop/similar. The RAM frequency will be automatically adjusted to "sync" to the CPU's frequency.