The more activity you have going on, and the better theg raphics you want, the more powerful a video card youll need. Do you need a monitor, mouse, keyboard too? if so, how big a monitor? gaming mouse and keyboard or a plain jane keyboard? Here are my specs for BF3 and I only get a little lag with Ultra graphic settings:
Intel i7-970 CPU Factory heatsink. no OC.
Gigabyte G1.Guerilla 1366 Socket
XFX Radeon 6870 1GB DDR5
G.Skill Sniper 1600 Triple channel 12.0 GB
Thermaltake blackwidow 850W PSU 80 Plus Bronze
2X 1TB Seagate HDD's 3.0gb/s (want to RAID them in a mirror configuration when I figure out the HDD issues I am putting my OS on, clicks in my machine, no other
)
NZXT Phantom case with 2X 200 mm, 1X230MM, 2X140MM, 2X 90mm.
Acer 23.6" moniter, 1080X1920 res
Regular logitech keyboard and mouse.