Get a Lenovo G-580. At 34k, it will give you an 3rd gen i5 @ 2.5-3.1 Ghz, 4 GB Ram, 500 GB HDD, 15.6 inch screen and Intel HD 4000 graphics. USB 3 is there, web cam is VGA but is quiet good for Video calling, pictures are quiet sharp.
I dont know about Mafia 2, but it plays GTA 3, Doom 3, UT...