My 5670 overclocked can hash at about 110MH/s max. Since the 6670 have 80 SP more, its hash rate is probably between 120-135.
They're not the same SP's. Efficiency for mining for the 6xxx series is a bit lower IIRC.
Even with the 3% bonus and such, a 900MHz (over 800MHz) 6670 won't push much past 110mhash/s