I doubt you could find a single GF6600GT performance review that does not contain Doom 3 benchies. So you should be able to gets loads of info on that.
I am guessing you are either very happy with your performance, or not at all happy. Maybe I am wrong and you don't own one yet. Anyway, remember, in D3, the rest of the system does matter alot too (CPU/RAM). Don't expect greatness out of a GF6600GT if you are running a AXP1800+ with 512MB or less of PC2100. But if you have a decent system, XP2700+, P4 800bus, or an A64, it should do very nice with that card. I'd expect 1024x768 High Quality with 8XAF. If you have a killer system, then 1280x1024 High 8XAF might be easily playable. Just my guesses based on reviews, no personal expereince with a 6600GT.
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