Memory Speed and Timing Have Little Effect On Computer Speed

I was doing some bench marks on my computer and noticed that I saw very little performance gain from upping my memory speed and timings.

gigabyte ds3l
e2160 @ 3.006 ghz
2 gb ddr2 800
3850 256 mb

Super Pi 1M:

668 mhz, 2.0 divider (1:1 ratio), 5-5-5-18 timings

1.8 ghz 32.265s
2.16 ghz 28.656s
2.52 ghz 24.797s
2.88 ghz 21.765s
3.0 ghz 21.218s

802 ghz 2.4 divider, 5-5-5-15 timings

3.0 ghz 21.094s

This is less than a 0.6% increase in speed. 3DMark06 score was 5 higher, that's right 5 (9373 to 9378), with the faster ram timings. My memory requires a increase in voltage to be stable at the faster timings. 1.8v @ 5-5-5-18 ... 1.9v @5-5-5-15. The memory is rated for 2.2v @ 4-4-4-12.

To me it makes no sense at all to increase the memory voltage and lower the timings and or increase the speed for at most a 1-2% increase in CPU speed. Which would then equate to a less than 1% increase in FPS.

Am I seeing this right or should I be getting more improvement out of my memory speeds and timings?

Also, I get a 3dmark06 score of 9373 with the above setup. Is this about right?

Thanks