When u do anyting out of the ordinary it almost always voids the warrenty. For example overclocking or flashing the bios(which has the same effect as overclocking). As soon as u do that ur warrenty is gone, because the card is being used different than its intent. Check the book the card came with it. I can't be sure though because i've never read there policy.

I disagree though, i think the graphics card would help. Put a card from 5-6 years in and it will not run as well as with a card from now.