Well, the i7 860 would be faster in single threaded applications because of its higher Turbo Boost, and will pretty much beat most processors in gaming. However, I'd get an ASUS P7P55D-E LX or Pro instead of the normal P7P55D-E vanilla motherboard. Gkay does have good suggestion though, the Core i5 750 2.66GHz should be plenty for gaming. As for chemical engineering, the Core i5 750 should handle any app. If you don't mind spending more, I'd get the i7 build, because really $100 can't upgrade an HD 5770 to an HD 5850.