1200x900 battlefield 3 budget graphic card

[Naozumi]

my pc specs is
intel core i3
RAM - 6GB
currently using ati radeon hd5450
psu - 300w only .
running windows 7 home premium .

i want to play battlefield 3 so bad in high specs in 1200x900 resolution . someone please help me...

 

[IRONBATMAN]

May I know your full PSU name ?