I am hoping to upgrade from my D700 to either a D800 or a D3S. I shoot a LOT of dance (low light action) and really need the higher (e.g. 3200) ISO range. The D700 is good to 1600. I would love to save $$ and get the D800 (also video capabilities), but don't know if it will be any better at higher ISO than the D700. Any thoughts?