That sounds like you have covered most bases. Just to be sure that the system isn't bogged down with background tasks, check System Configuration/Start Up and see how many boxes you have checked.
Then run CCleaner to clean up resource wasting crap and registry errors. http://www.piriform.com/ccleaner
At 720p, you should be flying with those 2 GTX 660s. I have a pair of GTX 660 OC cards in the rig in my sig. And our processors should be fairly comparable when it comes to gaming.
What is your 3DMark11 score? I'll compare it to mine.