For the GeForce drivers version...don't look at the very first numbers (beginning with 4). Rather, look at the last four which should be in your case .0647 or something along those lines.
I'm personally running the 6.31 drivers. Had a friend upgrade to the newer ones and then immediately notice a 13fps drop in Q3 benchmark scores. Not sure if it was just a freak accident on his part or something clashing between the new Det's and DX8.0. Either way I didn't feel like taking the chance, so I'm sticking with 6.31 and DX8.0 for now...everything seems to be working fine for me.