You already have a 7870. I'd keep that until Nov 2013 and then try to sell it. By then, new Nvidia 7xx will be released. Just this week Nvidia released a 780. Also, AMD is gonna release new GPUs, but they are not a big improvement on the 7xxx series.
I too love BF3, so I'm gonna wait and see what the reviews say about GPUs performance in BF4 before I decide whether to sell my 660ti or keep it.
the 7870 is a solid card. I'm running off one right now. and, of course, I don't have cash to throw at a new GPU. However, I'd hold onto that 7870 until we know more about AMD's next series, because their next lineup of GPUs may be a new architecture and a die-shrink. That's a recipe for some really good performance improvements - along the lines of 50 to 100 percent better.
awesome! thats what i plan to do Keep my card and see how it runs bf4, then decide!, how much can i push my card in the area of overclocking? i have it set to 1125 of Gpu clock speed... any further?
If you've already reached a good overclock and it is stable then I'd leave it as is. At some point you won't get much of an improvement. However, if you do want to then I'd google your gpu and see how others have overclocked it.
Hard to answer. I don't know what a typical value would be. I use software to monitor my temps and it also monitors CPU usage. But it only records current and peak. And the peak value isn't accurate, cuz a sudden spike will hit 100% but it is just a freak occurrence.
Your original question was about bottle-necking. Your i5 will not bottleneck BF3 and I'm 100% sure it won't bottle-neck BF4 once it is released. The GPU is really the only thing that will in your build.
The Amd cards released in Q3 or Q4 of 2013 will most likely be a new architecture using a 20nm process. The 8000 series is just OEM and laptop only. If you want to hold on to your 7870 and play bf4 for a bit then upgrade to a 9970, it doesn't sound like a bad idea. If AMD does this correctly, a die shrink and new architecture should destroy the 780. The leaked specs seem to be 2x the 7970.