I7 980x @ 4.5ghz
Crossfire 5970 @ 1ghz core, 6ghz memory(Well, Quad SLI GTX 480's would do better, but the PSU would be over the max wattage for a normal wall socket)
24GB 2400mhz DDR3
6 intel 160GB SSDs in Raid 0
Some high end mobo
1200W PSU from a good company
There's the essential parts for the best gaming computer, I believe.
I would make the question a little more detailed if you want a better answer then "The Best".
Maybe you can tell us whether you want AMD/Intel or how much money can go into the build?
Wow, you have four GTX 470s on a 1200W? How high is that 980x overclocked?
You could still do better with more SSDs for load times, but otherwise that thing has to be a monster. Have you fed it Crysis for breakfast?