The i5-3570K is the "sweet spot" CPU right now. Anything above that is diminishing returns and I would recommend saving the $ for a future vidcard upgrade. Besides, even this CPU is slightly ahead of the curve compared to your current vidcard so you'll just be dealing with the same bottleneck either way.
$229 CPU: $118 Mobo: $ 41 RAM: ----- $389
That's more or less the "everyday" deal.
Now if you're willing to find a way to purchase at Micro Center in Chicago, you can get the same CPU, the same mobo, and the RAM (from NewEgg) for $271 (+ tax on the CPU/mobo).
This all assumes you don't want/need CrossFire capability (I have never liked the value/flexibility proposition of xfire/SLi rigs). If you want/need that, or want/need more USB3/SATAIII ports (the mobo I linked has two of each) then another $20-$30 will get you a mobo with that.
All that said, if you're willing to wait for Black Friday AND go to Micro Center in Chicago, there's a good chance they'll repeat their smokin deal from last year which would basically cut another $20/$30 off the already low price they offer as part of their combos.
If you have your heart set on spending more, then the is the next rung up for +$100. On the motherboard side, the next logical rung up is a for $150AR. It has a few more SATAIII and USB3 ports, and you get a UEFI BIOS and a bit better quality components.
But I firmly believe the better value is to save the $100 and look at upgrading your vidcard down the road. The Micro Center deal above for $271 plus for $247AR is an incredibly good value. Total bill of goods assuming the (non-BF) Micro Center trip and the vidcard would be $518 (+ tax on the mobo/CPU).
That would net you between a 50% and 75% improvement in game performance on the vidcard alone (per ).
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