Minecraft, guild wars, bf3 maybe some arma 2. I would like to play on the highest settings if possible. What would you suggest to do this?
You won't get very smooth gameplay with a 7850 on a 1920x1080 resolution. Look at these benchmarks
BF3 will be playable on medium/high settings, but if want your game to run smoothly on ultra settings I would invest in something like a GTX 670 (if you have enough money, of course). Otherwise, that 7850 will be fine for running BF3 on reduced settings.