Is anyone aware of how much mining stock wattage varies between the models? I have heard everything between 125W to 350+W but I'm considering picking up a second card in the case that it's closer to the former...
That depends on what voltages you're running at. I've heard of people undervolting and underclocking their 7970s down to 60W. Upwards of 350W would have to be pretty hefty overvolted and OC'd.