I was running at 49fps average with 1 card before though. Also, I play games with much higher end graphics over 100fps, why would this game bring down my fps? It doesn't look nearly as good or crisp as BF3 or Crysis.
The quality of the graphics means a lot less than A. the optimization of the game and B. what processes you are forcing it to perform. The Extreme AA in Sleeping Dogs is really damned demanding. Lower that to high and you should see immediate framerate increase.