I know its a old post but its the first one that comes up when searching 6670 hash rate in google.
Iv got a gigabyte stock oc edition, at 820mhz pumps out 105mh/s Can over clock to 905mhz (920 gives artifacts) which works fine in games and pumps out 127mh/s but throws a vpu restart error with in 20mins all the way down to 880mhz. So have to run 875mhz which pumps out 119mh/s.

So quite disappointed in the card. But oh well only cost me $150nzd including postage. And the options were limited since this is my GF's computer and only has 300W PSU and has to remain silent since its in the bed room. And its only drawing 209W full load.