Hello,
I play on a q6600@default, 4gb, hd6950 2gb, win 7-64 bit.
I'm happy about the performce I have with my settings but was wondering if I could be able to improve image quality some more without crippling my performances.
This are my settings, what would you change?

you have a great gpu card, so you can enable AA, and push Light/shadow/DOF CIN and memory texture to Ultra. Your performance won't change

We should not make 400 threads about the same topic :D

go here
http://www.gog.com/en/forum/the_witcher_2/official_performance_optimization_and_graphics_customization_thread

Do you have one of those hd6950 that you could mod to a hd6870 level?