How much memory is needed in a video card if...?

lets say a person has 8 gigs of ddr 3 ram, would a 1gb gpu make much of a difference compared to the same card with 512mb when gaming?|||makes a difference in speed and dedicated memory where if you have the 1 GB then you can play new games in the future as well. Check specs as new cards are coming out and what features you want on the card.|||ya 1gb is better obviously, but with 8 gigs of ram, you should be fine, but in the future 512 will never be enough, so 1gb is a necessary thing