Looks good, most games are GPU bound so the slightly lesser CPU isn't a problem.
Get 8GB RAM rather than 4GB to have slightly smoother experience and you are on to a winner.
GeForce GTX 560 or a Radeon HD 6870 are about on par performance wise.
Bit more money you can get Radeon HD 6950 2 GB which is around £200-210. If you are willing to spend up to £300 then the GeForce GTX 570 would be a good option (I would get the 570 over the 580, don't think the 580 justifies the cost), better option instead of the 580 would be 2 x Radeon HD 6870 in CrossFire or 2 x GeForce GTX 560 in SLI (which outperforms the 580 while costing less).
I really want a nice shiny rig but can't be arsed with the self building bollocks. I was looking at cyberpower website but I always get carried away and the rigs end up costing well over £1k. I don't har that sort of money, don't want a 36 month finance and not too sure I can afford £100 a month for the 10 month finance option.
Guess I'll just have to try saving!
Or I could spend £150 on some ram and a gfx card and make do for a while
"USP'd in the face from miles away Peter. You should be embarrassed." - Floodie 13/03/2012