AGP aperture question?

If I set my AGP aperture to 256mb instead of 128mb will my computer play games and videos that normally lag smoother? My computer can not play the HD videos on youtube, or some games without lag, just curious if this will solve my probs, or lessen them. I only have 1gb of physical memory, but at idle my PF usage sits around 170mb, and lower at startup so no prob there.