get the AMD and flip out for a Phenom II... the WC setup wont benefit a Q9300 (because the FSB will limit you before temp ever will) and you wont have to shell out for good DDR3... the q9300 is a decent chip, but you'll need alot of patience and a bit of skill to get it stable enough to get good benchmark results... the 940, however, can be OCed to over 4.5GHz on water with a decent level of stability (mind you that's not exactly easy)
so even though you'll probably get better clock for clock performance with the yorkie, the extra speed will more than make up for that gap
Why you are comparing 940 to Q9300, when Q9400 is cheaper than 940 ?