The E-670 is one nice unit. Congrats and good luck with it.
I have an S-330. The sear station burner is a forth burner, located in between the far left and center burners. If you turn those 3 burners up to high, you get a very hot area centered around the sear station burner, on the left side.
Yours looks to work the same way, but in the middle.
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I was at my favorite, local Weber distributor yesterday (5/9/12). They have an S-670 on display. I looked at it and I was right. The sear station burner is an extra burner located in between the two center burners. When those 3 are turned up to high, you will get a very hot spot in the middle of your grill.
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Bob