One things that has helped my performance a lot is unparking my CPU cores.
http://www.youtube.com/watch?v=ulm-PeZxi0Y
Check the description, as I linked the utility and a quick howto. Give it a shot, you can always revert back easily.
This - i cannot recommend this stuff more (and gotta eat my hat too, cause i was sceptical at start). If you are sceptical just see for yourself as in video ( command needed is perfoverlay.enablegraph and also enable fps display).
In my case ( 4770K @ 4.5Ghz and 780Gtx playing 1920x1200 on ultra) i was supposedly getting good performance - 60FPS with occasional drops of FPS into ~45-50 range. I though it was due to multiplayer blabla...
NOT SO. I turned on perfgraph, and guess what, spikes are caused by CPU taking 75ms to render some frames, sure they are rare, but you can die several times in 75ms and jitter is bad for health.
After disabling core parking i am now getting rock solid 60FPS, without any dips, just solid performance. CPU frame time can still overshoot 16.666ms required for 60FPS during action, but it's 20ms, not 75ms now!