I would say medium settings or low as my system is better than that (not much better if I am honest) and I can run battlefield (say game engine) on medium.
CPU - Intel Core I5
GPU - nVidia GeForce 260 GTX
RAM - 2x 2GB DDR3SmasherG;607523
Thanks for the answer, I found someone on youtube with the same CPU and RAM that I mentioned, but with a Nvidia Geforce GT 240 1GB DDR3 128 Bit and running it with all settings on ultra (except he has shadows on high) on 1280x1024 and getting 20-30 fps.
My monitor's max res. is 1024x768, the GTS 450 1GB DDR5 should do the trick.