to play multiplayer you will need a quad core to play smoothly also your gfx wont give you high or ultra. it will give a mix of high and medium. dont forget to turn blur off or you will incur a heavy hit on the gpu.
the 7750 isnt a strong gfx card. its low midrange but should work well enough on your small screen. as far as gaming goes. it will max out a lot of older titles like call of duty 4,5,6 @720p but bf3 punishes even the best cards due to poor clipping on some maps.
but like i said your cpu will likely cause the biggest issue as the frostbite engine needs a quad to run smoothly or it wont let you max out the performance of even the most poultry of cards. a gtx 270 for instance ( a good card 3 years ago) will bounce between 40 and 5 fps when paired with a dual core on bf3 but will give 125 fps solid on cod 4.