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Despite all those newegg 'reviews' its quality is not known, as I doubt that any of them have put a full load on it and measured its performance. And I'm not aware of any other technical reviews of that nature.

Intel i7-920 3.33GHz 15/12/2010
http://www.anandtech.com/show/4061/amds-radeon-hd-6970-radeon-hd-6950/24
6850 Crossfire Power Consumption:
Idle = 170W, Load - Crysis = 378, Load - Furmark = 423W
These numbers clearly show that even a good 550W PSU can easily cope with two 6850s.

Any of these would be better as they are known to be reasonably high quality:
Rosewill Green Series 630W 80Plus $60
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182200

Antec High Current Gamer HCG-520 80Plus Bronze $64...
A good 600-650W power supply would be OK but that one has only 23A on each of the 2 12V rails while a corsair TX650 V2 has 52A on a single rail which would be fine. Basically crossfire would be a no on that PSU it might run (it might not) but you would be taking a big risk.
 
Despite all those newegg 'reviews' its quality is not known, as I doubt that any of them have put a full load on it and measured its performance. And I'm not aware of any other technical reviews of that nature.

Intel i7-920 3.33GHz 15/12/2010
http://www.anandtech.com/show/4061/amds-radeon-hd-6970-radeon-hd-6950/24
6850 Crossfire Power Consumption:
Idle = 170W, Load - Crysis = 378, Load - Furmark = 423W
These numbers clearly show that even a good 550W PSU can easily cope with two 6850s.

Any of these would be better as they are known to be reasonably high quality:
Rosewill Green Series 630W 80Plus $60
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182200

Antec High Current Gamer HCG-520 80Plus Bronze $64
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371047

Seasonic S12II Bronze 520W $60
http://www.newegg.com/Product/Product.aspx?Item=N82E16817151094

XFX Pro 550W Core Edition 80Plus Bronze $70 ($15 rebate, $6 shipping)
http://www.newegg.com/Product/Product.aspx?Item=N82E16817207013

Antec Earthwatts Green EA-650 80Plus Bronze $70 ($20 rebate)
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371044

Rosewill Hive 550W 80Plus Bronze Modular $70
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182131
Apparently based on the same internal design as the OCZ ZS series.
 
Solution