Sir, this is completely incorrect on every single level.
You can have a 3" screen, or a 120" screen. If they are at the same resolution then they will use the EXACT same amount of memory.
The resolution is what matters, the physical size has NO EFFECT on how much VRAM is to be used.
630 GT 4GB + windows 7 64 bits(32 bits will bottleneck) = best performance for such large screens as 46" and even to 84" ones.