Getting a gaming rig. Buy or Build?

[Squilliam]

http://www.guru3d.com/article/vga-charts-december-2009/2

I would suggest you take a good look, especially taking note of the relative positions of the 5850 and 4890 in games where the graphs are steep as this indicates the game has a graphics bottleneck.

Also two things to take note of:

1. HD 5xxx series are DX11 which means more efficiency, better image quality etc.
2. HD 5xxx series support Eyefinity (you can use up to 6 monitors as if they are one panel) and display port for future connectivity.