I have the feeling i gained some fps by putting: -cpuCount=4 -exThreads=3
as starting parameters within steam.
My Specs are:
q6600@3,0ghz (quadcore without hyperthreading thats why i put cpu count=4 and extra Threads 3)
8 gig
ssd
and an 7870
win 8 64
Its hard to say if there was a real improvement or it was just my imagination, but try it if you havent yet...