The likes of the 178+, or even 175+, drivers, are not ~particularly~ aimed at dev for cards in the 8 series. Sure they'll work, mostly down the "support" line, in so much as they'll work but they aren't going to massively increase performance in any way.
Generally those drivers will be of ~some~ benefit to 9 series users, but will be more emphasizing GT200 users. As will the 180+ releases, lesser so the 9 series with these perhaps. All along they will still "support" the 8 series as they do the 7 series etc.
As I know the big push for the newest drivers are going to be the desire to use physx maybe, it would be a good idea to find a physx set of nvidia drivers that work and stick with them as a base. When new drivers come out, try them, if they crap ur system, revert to the base ones.
174++ are the drivers to stick to tho, cos there was a god-awful bunch of mistakes made in the 169 sets that gave lots of ctd to alot of peoples cards - particularly temperamental to performance or oc setups.
To be sure the current drivers u have are fully installed properly, u can open the nVidia control panel, and in the bottom left corner will be a link that says "system information". If u click on it a window will open - if u then click on the "component" tab, it'll list all the versions of the driver-files installed on ur pc. If u have Driverset 178.13, it should read 126.96.36.199.13 on all of them, possibly with the exception of the control-panel drivers (they dont matter as much, theyre seperate). If some of the files are different values, then u have mixed driver files, which means u need to uninstall them and remove the files (with DriverCleanerPro or similar) b4 reinstalling the ones u want.