Whenever I used Coolbits2.0 Auto-Overclocking, usually the GPU and RAM frequency jump at least 50mhz for the GPU and 75-100mhz for the RAM, but that's when the card runs at stock speed from the manufacturer.
Nowadays, almost every nVidia card you buy is already slightly overclock and perhaps yours is not clocking any higher due to that? you guessed it! it's already overclock from the manufacturer.
There are always the possibilities that the card can and will overclock a little more but it would depend. Try overclocking the card as much as you can and run 3DMark and if you see a little or a lot of artifacts during the 2nd test, that means the card can't handle it, you're going to have to underclock it a few mhz.
BTW, you can stop 3DMark by pressing ESC and do the necessary adjustments.
One thing I forgot to mention is that the 83.40 drivers are not that good. Best are 81.95 or 81.98. For some odd reason the score in 3DMark with the 83.40 is lower by 100 points then the 81.95 or 81.98. I still am running 83.40 but will reverse to 81.95.