Dell XPS 8300
i-7 2600 @ 3.4
8Gb's of Ram
GTX 560 ti
( The PC came with a 6770 but I recently upgraded to a 560 ti )
If you have a really low resolution monitor maybe you can squeeze a playable framerate out of it, but at 1920x1080 I really doubt it. Since the most important thing is to keep a high framerate (60+) I think something like high/medium should be fine
Depends on the resolution at 1920X1080 not really the framerates would be horrible. Medium if you want a solid 60FPS if you can accept a bit less or some dips then set some things to high. When your playing BF3 though there is honestly little visible difference between med/high/ultra its only really watching gameplay videos afterward you can easily pick out the extra visual awesomeness.
I'd say high settings for solid 60 fps. At ultra, you'll be having 30-40 fps, which is really not smooth and pretty impossible to shoot people at that.