With a 6850 I would stick to medium/high settings. Running ultra is nice but it is not a must to enjoy the game details. The aformentioned comments already covered most of the points but I think a gpu upgrade would benefit you more than upgrading the fx-4100. As for whoever told you that it could run bf3 on ultra, if it was a salesman at a retail store most of the time those people don't have a clue and just say yes or they don't realize what resolution you are running. If you are running under 1080p then the 6850 will sustain fps rates on those high/ultra settings much easier. Always ask or research online for questions like that. You have to ask yourself if you really need ultra on your current configuration. If you upgrade your cpu and/or gpu, then by all means rock it out