The GTX 680 is considered the high end single GPU card of the GTX 600 series, but the GTX 670 is indiscernably close despite using less power and being much cheaper.
The 680 is faster than the 670. Passmark is a synthetic benchmark that is not always representative of how games will perform (actually, it's rarely helpful much at all)
There probably won't be any new high end cards in the GTX 600 series.
The GTX 700 series will probably succeed the GTX 600 series.
Is there any announced release date on the GTX 700? Would it be reasonable to wait for the 700 series instead of getting a 680?