H61 / H67 + 2400 (quad core). Should be able to fit in the budget, while still leaving enough for a decent GPU. Enough for BF3 anyway. A 2400 is faster than an heavily overclocked AMD 955BE, so save yourself the trouble.
In short, your build, with a i5-2400. Can get a 500GB drive to save a bit of money or tweak components.
Note that H61 / H67 can only go up to 1333MHz RAM. But the price of the 12800C9 HyperX is good so why not.
Finally, I prefer the Antec TP-550 over any OCZ.