I would just not use max settings, lower AA and AF, you don't need them at 16x (I don't know what the max is in TF2 though.)

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Something is wrong, I have a slightly better processor ( q9450@ oc 3ghz) but my 8800gts 512 is a lot worse then what you have and my game runs at a constant 60fps with everything maxed.
By everything maxed I mean everything you can set from the menu because there are some console commands to make it look prettier but I didn't touch those.

Its because the source engine is very cpu dependent, rather than graphics card, so most gamers tend to have abnormal fps on TF2 because they favour the graphics card over the cpu.

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a bird in a bird in a bird in a bird in a bird in a pig