At higher resolution as 1600x1050 you will decrease the bottleneckig as the GPU is working more than the CPU, I had an 6570 DDR3 with an AthlonII x2 260 3.2Ghz(overclocked 3.6ghz) and i played many games (wow at high, crysis 2 at casual) everything at 1440x900 with 50fps on WoW as regular and with crysis payable (dont know the actual fps)
But! we have to say, that your PSU is "enough" for the Wattage and it also have a PCIe 6pin conector, so you will handle your GPU well. BUT, this comes the bad part, CoolerMaster is well known for their good cooling but no for PSU's (those are not realiable and pretty bad). In the near future when you upgrade your mobo and cpu, also think about a new PSU, for now you are good since the only "heavy" load to your PSU will be the HD6850.
With a HD6850 you will get good FPS and WoW and other games... !