I have a 4 or 5 year old ATI 5870, no problems with BF3 on HIGH 1920x1200
Getting that card for a 1440 res leads me to believe you think the video card is all that is important. Tell us what other hardware you have in that machine and we will tell you the reason game is running slow. I bet you have a bad CPU.
Did you just read random words from his post? He clearly listed his hardware.......