You have a high end requirement and you clearly don't understand how these things work.  You asked if your PSU could handle it and the answer is no.
The ATX2.2 standard dictates that the 12V2 rail is DEDICATED TO THE CPU (not GPU).  Meaning you have to power the whole of the rest of your system with 12V1 (17A) = insufficient.
Put it this way.  12V2 is only for the CPU.  It cannot share the underutilised power.  Therefore the graphics card, hard drives, fans and so on all require power from 12V1 which is rated at 17A.  BTW at 17A it shuts down.
The 260 requires up to 15A just by itself according to nVidia.  That leaves less than 2A for all the rest of your system bar the CPU.
The 500W minimum that nVidia suggests is misleading because your 550W PSU for example 
can only provide 17A to the system (minus the CPU), where as something like the Corsair 520W 
can deliver 40A to the 12V rail due to its EPS 2.91 certification which your PSU lacks.  And the Corsair is rated at 30W less.
So as you can see, wattage is misleading, your PSU is underpowered and you need something like the Corsair I mentioned above. 
http://www.corsair.com/products/hx.aspx