My SLI system doesn't run it very well either, since the game did not support SLI out of the box, I'm not sure if they have patched things up now though.
Your system really isn't up to scratch, the min requirements always lie, you always need something a bit above to play it at decent settings with decent fps.
Your system is a bit lacking for that game, I don't know much about amd cpus but overclocking it as you said would help a little bit and the same with ram but I really doubt there would be much improvement unless you upgrade you system.
I might be changing mobo, ram and cpu soon to something more recent and I am looking to sell them in a bundle if you are interested.