Gaming vs. Video\photo editing

Assuming the application you use actually uses the video card for process. ( I hear only the latest adobe photoshop will actually do so) then they're both the same. The fastest gaming cards will be best for video editing. In older programs photo editing typically relies more on the processor.

Well personally I'd say wait until you know what's needed, things are still working their way out in editing. At this time for nVidia a Quadro card is required for the most intensive feature in Premiere and After Effects, while there is not this requirement for the ATi cards. This will likley change longer term (like initial PhysX support) where at launch they are forcusing on the professionals who pay top dollar for such rigs, then bring support to the masses.

For Photoshop it's any OGL 2.0 / SM3.0 card that can aid effects and transition processing through OpenGL.

So considering what you're looking as mentioned the top gaming cards should offer you top editing too, but I would say avoid any Geforce 9xxx series or earlier, even the GX2 in this case, and stick to the HD4K and GTX series cards due to their ability to handle double precision calculations, as well as improved single precision.