Quote:
Originally Posted by
Tslm 
AM3+ isn't ever going to have PCI3 or native USB3. It's an extremely dated platform that's only still around for the sake of compatibility and the fact AMD don't want to invest in a new chipset. The PCIE controller is still on the mobo with AM3+. I don't see the point in an FX-4300 when a 5800K is the same thing minus the L3 cache, and if you look at benchmarks L3 is mostly useless for consumer workloads (AMD also said this in a tech blog prior to Bulldozer being released - L3 is server workloads mostly). The only advantage to AM3+ would be 6/8 core cpus and the fact that there are no FM2 boards that will allow 3 graphics cards (not that you care).
A 5800K is basically as good as a 4300 aside from the fact it won't overclock as far. One thing I should mention is that both the 4300 and 5800K might not be adequate for BF3 mp. I remember playing it on a 4100 and it was not smooth at all. If you're deadset on BF3, AM3+ and a 6300 is your best bet. If you can live without absolute smoothness in that one game, I'd suggest FM2 with a 5800K.
edit: A 7870 is a really nice balanced card to go with whatever you choose, so I'd suggest keeping that
gaming is where the L3 cache makes some difference it seems,
http://www.anandtech.com/bench/Product/700?vs=675
as for the OP, if you really want to go with AMD, go with the FX 6300
