The case is your choice but I would suggest the cm 690 2 advanced.
For the cpu,a phenom 2 x6 1055t or an i5 750 would be better since both are great clockers and perform phenomenally with an oc to 3.8-4.0ghz.
The mobo is overpriced but supports trifire at x16/x8/x8 so it is ok.
For the gpu you should get 2 6850s instead.Although you will lose future upgradeability in the form of a third gpu by the time it is required 2 5870s will be inadequate anyway.
The psu is ok and should support the 2 6850s easily.
For the ram I don't think 8gb are needed for a gaming system but since it fits the budget and they're nicely priced they're a neat option.
For the hdd I suggest you choose a larger hdd as 500gb usually aren't enough if you store everything on them.At least for me;p
PS.If your budget is 1300$ you should consider a good cooler too like the corsair a70.
That's all from me;p
Crazy expensive mobo. For that money on combined CPU+mobo you should be moving to an i5-760 based build or dropping to a cheaper AMD mobo.
The 5870 makes no sense now that the 6870 is out. The 5870 is ~38% more expensive (after MIR!), but only 8% faster. When you put them in crossfire, the 6870 scales much better than the 5XXX series and beats dual 5870s.
The OCZ PSU sucks (check the Hardocp/JohnnyGuru reviews, it failed violently at ~650 watts, and had unstable output). Here's a high-end PSU 750 watt, but it is more expensive. http://www.newegg.com/Product/Product.aspx?Item=N82E168... Easily the best in class for 750 watts besides the Seasonic (therefore Corsair) gold series for ~180$.
You don't really need more than a 650 watt for 6870 crossfire, but it's hard to find really solid 650 watts that are priced well.