I think you will be able to play at low-settings but full resolution with 35~50fps without delay or lag. If you are thinking about buy a new graphics card, wait NVIDIA release the GTX 8xx series, and the prices of the past graphics card might decrease.
Any NVIDIA GPU with at least 800 CUDA cores will be good to go.
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B85-PLUS or B85-PRO GAMER is just fine! You do not need more.