Just a slight update to the rig. I've installed an OCZ Vertex 2 SSD, which has improved speed and performance ALOT.
Here's a benchmark comparison of the SSD compared to a 1TB Samsung drive. You'll notice it's the random 4K reads and writes that suffer the most on the HDD.
And here's the previous and current performance index marks. The hard drive is still the lowest score, but it's much closer to the performance level of the CPU/RAM/GFX.
Previous Performance Index:
Current Performance Index: