I've been through Every Newegg and Amazon card as well as Tiger Direct, Microcenter and Fry's.
I can't find a single 7970 that has unlocked voltages.
I'm going 7950 I guess.
actually I just got two of powercolor 7970 V3, and they have unclocked voltage and with dual fan configuration it mines very quite
the only drawback is I haven't been able to mine LTC over 550Kh/s