Please advice!! GPU for AMD Phenom

I want to buy a graphic card specifications as under-

AMD PHENOM II X4 925
2.8 GHZ
2 gb ram DDR3
on board nvidia Ge Force 6150 se nForce
approx memory-793 mb
current resoultion- 1600*900
games i want to play- nfs hot pursuit 2010, COD BLACK OPS, assasin creed 3
budget is around 300 rupees/ approx 60$
which one should i go for ATI or Nvidia?
please help im just a starter