Is this power supply sufficient enough to power quad 7970s?

Yes!

Yes , however if I were spending $250 I would get this psu.

SeaSonic X-1250 1250W ATX12V / EPS12V SLI Ready 80 PLUS GOLD Certified Full Modular Active PFC Power Supply
$249.99
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

+1^

Ok, after doing some research, it seems the SeaSonic is a better power supply. I'll go with that one!

I have the Seasonic 1250w myself and I love it.

Good choice.

The XFX ProSeries 1250W Black Edition uses the same internal design as the Seasonic X-1250. The only difference between them, apart from appearance is that the Seasonic uses a 12cm Sanyo Denki San Ace, Ball bearing and the XFX uses a 13.5cm Protechnic Electric MGA13512YF-O25, FDB fan.

I guess that's why the XFX costs $2 more.

So does that mean the XFX is better?

No it means that XFX is a Seasonic with a XFX wrapper.