I built my own machine in 2011. I will probably do some upgrades soon, but it works well enough. It is Windows based, so it may not be what you are thinking. One thing that may be relevant across the different machines is that I've noticed that processing is much faster when I am working off my SSD card rather then my hard drive. The read/write speeds are supposed to be faster and it is noticeable.

But my machine has:
  • AMD Quad Core Athlon 3.0 GHZ
  • 8 GB RAM
  • 2 x 1.5 TB Western Digital Black
  • 128 GB OCZ SSD