Sorry if this is a stupid question but can someone provide a basic overview of how much impact memory timing has on system performance. I'm running my DS3 at a mild overclock with the clock frequency increased from 266 to 320 Mhz so my E6600 is running at 2.88GHz. I've also set the memory multiplier (or whatever it's called) to 2.66 so my Corsair XMS 6400C4 memory is running at 851MHz (51Mhz over the stock speed of 800MHz). I have all of the memory parameters in BIOS set to auto except for the DIMM voltage which is set to +0.2 so the memory is running at 2.0 volts.

When I check the memory settings using CPU-Z it indicates that the memory timings are set to 5-6-6-20 whereas the memory is rated to run at 4-4-4-12. The system seems to be running perfectly at the current settings but I'm wondering if it's worth the trouble to try running the memory at a slower speed (i.e. change the multiplier to 2.5 so the memory is running at 800Mhz) and start playing around with the settings for timing or is it better to run it at the faster speed with the current timings.

Thanks in advance for your help and I'm sorry if I got any of the terminology wrong (I'm new to overclocking and still trying to make sense of all the variables involved).