Core Clock Speed

Is there much difference in a video card with a clock core of 670MHz. versus one with 650MHz ? The reason I asked is because I purchased an 8800GTS 512MB card that was suppose to have a clock core setting of 670MHz. When in fact its only 650MHz. Is that a big enough difference to make a fuss over or should I just be satisfied. Any answer would be greatly appreciated and thanks in advance.

20mhz can make a huge difference in core clock. As you push it higher, the performance increase is exponential. If you push from a default clock of 600 to 620 you might not see a huge jump, but if you push from 620 - 640 you'll see a definite jump. Even more so from 640 - 660. My 4850 came overclocked from 625MHz to 675. Ive since pushed it to 710mhz. The framerate jump differs from a 10FPS increase in Crysis, to upwards of 20 - 30 in CoD4. Although those are subjective analyses, they represent a very tangible performance increase.

I also have an 8800gts 512mb, just download nvidia's ntune and overclock it yourself. Mine is at 770 core, but I run it at 100% fan speed when I game.

Thank you very much for a most accurate and detailed response mcnuggettodeath. My hunch was correct then. I'm most greatful for you and coozie7's answers. I just didn't realize how much of a difference there was. I mean one can tell by looking at the numbers there is a difference but I don't nearly understand clock speed, shader clock and memory like you'll and probably never will. I'm using the EVGA Precision Tool in order to overclock. The BIOS in my computer which is a Dell Xps/410 won't let you make but only a few changes because it's proprietary to keep people like myself from voiding their warranty by damaging the computer I would imagine. But it's mine I should be able to do as I please.