2nd generation Intel Core i3/5 Mobile Processors have a feature where the laptop switches between the dedicated gpu (GT 520m) and the intel HD graphics to save energy and increase battery life.
The dedicated GPU should still be used in games/graphic intensive applications...
I would recommend:
gt 440
http://www.newegg.com/Product/Product.aspx...N82E16814500192
athlon ii x4
http://www.newegg.com/Product/Product.aspx...N82E16819103871