for your budget, i suggest you check out the SONY VAIO E Series http://wuggee.com/laptop/sony-vaio-e-series-sve1712bcxb.html this machine can definitely play the most demanding games at medium settings.
specs include:
2.5 GHz Intel Core i5-3210M
6 GB DDR3 1600 RAM
7.05 lbs
500 GB hard drive
AMD Radeon HD 7650M