Unlikely, the way to increace you clocks is it voltmod the card itself. What you may find is that you get better performance when upping the PCI-E freq though. If I have OCd my CPU, if I leave the PCI-E freq at 100 instead of 105, I drop 20fps in 3d applications.
I'd say the 8 series, does a pretty good job for stock cooling, even with overclocking. It would be necessary for an aftermarket, if for some reason, your graphic card is above the norm or doing very heavy overclocking.