Yeah... 2 GTX 280s require atleast a 1200w PSU so 2 GTX260s will require atleast a 1000w maybe more. Also 1 GTX280 needs more cooling than an open-air set up can allow, you can bet your life that 2 GTX260 will be even worse. No, do NOT step up unless you plan on spending $200 for the cards, $300-$400 for the PSU, $100-$300 for a case with amazing cooling, then another $100 for insanely powerful and loud fans. At that point you might as well just take the side panel off your case and have a 30" industrial fan going full blast into it, about the same. Then you can enjoy your 5 FPS increase, lol