If you are looking into a gaming laptop, I would lean toward an AMD, only because the core duo's aren't the best gamers. You could get this and upgrade the RAM. It would be in your budget.
http://www.newegg.com/Product/Produc...82E16834115218
2 x
http://www.newegg.com/Product/Produc...82E16820145518
Or, you could spend the extra money and get 2 GB of RAM standard and get a faster CPU as well.
http://www.newegg.com/Product/Produc...82E16834115221
There is an open box version to save more money.
http://www.newegg.com/Product/Produc...2E16834115221R
The Mobility Radeon X700, with 128 MB of video memory, should be fine.