For around $500 you are not going to find a laptop with 8GB of RAM and good graphics.
Based on what is available at Newegg.com you basically have two choices. Both have the Radeon HD 8750 and 4GB of RAM. The good thing about RAM is that you can upgrade it later when you have money for it. Both have the same price of $530 and overall the same specs.
The main difference seems to revolve around the RAM. The Acer has 4GB of embedded (you cannot replace it), and a single slot for you to add one more stick of RAM. The Acer supports a total of 12GB. The Lenovo has 2 RAM slots, but it seems only 4GB RAM modules are supported since the official max RAM for the laptop is 8GB. The Lenovo comes with 1 stick of 4GB RAM installed.
The Radeon HD 8750m is considered pretty decent for a mainstream graphics chip. It is about equal to a nVidia GT 640m / GT 735m. How will it run GTA 5? Unknown. The game probably will not be released for another 7 months or so based on when the PC version of GTA 4 was released.