Sorted through a few problems with my new build, but now its running fine other than the fact that I'm getting terrible Vantage scores and IMO less than desirable gaming performance. My current specs are below:
Mobo: Gigabyte X48-DS4
RAM: 4gb of DDR2-800mhz Mushkin
CPU: E8500 (Non OC)
PSU: Corsair tx750w
GPU: HD4870 (OC'd to the maximmum on CCC, Temps on full load never go above 60deg)
When running 3dmark Vantage on "Performance" I'm only receiving a score in the low 8000s, and even on Medium settings, Crysis is terrible at 1920x1200. Obviously I'm leaning towards my CPU being the bottleneck, but even at stock speeds, I feel my computer should be performing much better.
The 4870 responds VERY well to increases to CPU speeds. I have the same CPU, and same videocard (2 of them actually), and i'm stock right now but when I tinkered with a very mild overclock (GPU clock/memory speeds at stock), I saw great returns in 3DMV.
Try just a mild OC to test it out. Should see your scores increase quite nicely.