Why, are you planning on SLIing them? The official recommendation from nVidia is a 400W PSU with at least +12V@26A. Either of the units I recommended are more than sufficient. In any case, the amperage on the +12V line is more important than the total wattage. Comparing the units in that regard:prob need something closer or more then 600 w
Pc Power & Cooling Turbo-cool 1 Kw.
Pc Power & Cooling Silencer 750/ 750 Quad.
budget preferably under $80