@hellfire24 not all asus gtx 670s can be overclocked to the top level, some people were able to do it, some weren't. I have seen some threads people complaining about not being able to overclock their gtx 670 to the Top clocks.
@OP it really depends on the rest of your system imo. If the rest of your system don't bottleneck that gpu, you should be fine. You wouldn't know for sure unless you test it out. Also make sure you dont install gpu tweak from the driver cd make sure to download and install it directly from the Asus website.