Hey, i want to know if the core i5 3570k will run BF3 smoothly at stock speeds or if OC will be needed.
More aboutcore 3570k
It will run assuming you have a decent GPU smoothly med-high settings with some AA.
Integrated, probably on low with AA off or near there.
Whether BF3 will run smoothly will also depend upon your choice of graphics card(s). By itself the 3570k will flounder at most games. If purchasing a k processor, you'll want to overclock - only real reason to buy the k. Will it make a perceptable difference in BF3? I believe so, but how much will depend upon graphics card choice. I know, not much help...