COD4,5,6,7

Well COD isn't really demanding so any of these cards will be able to rip through the game. So really this is how much you want to spend on the card, it also depending if you want to overclock, that's where most of the 460 and 6850 potential is

Are you referring to call of duty?Or a computational theory?

You are a little limited with that 500W PSU, the 5770 is not as good but would be a bit safer with that PSU.

The HD 6850 would be great choice, but you will be a bit tight with only 500W and not good brand is well.

So if you can get the 6850 for now and then after that buy better PSU. Somethink like 650W or better for crossfire in future - 750W

I have enough I like the gtx 460, I'd did a watt calc and it said I needed 483 watts

Well i didnt say 500W isnt enough but the thing is that the brand is not good wich means it says its 500W but it could accualy give only 400W.

But to be at the save side OCZ or CORSAIR (600W) would be the way to go.

Go for a corsair 500w builder edition PSU. It is cheap and good for your build. Go for the hd6850.