EVGA Classified SR2
Intel Xeon 5650 x2
EVGA Gefore GTX 590 x4
Throw a few SSD's and some 3D compatible monitors and you have a rig and a half.
Sorry you didn't specify a budget and you asked for the best
Asus Rampage IV Extreme Edition
4x watercooled 7970's in quad crossfire
64gb quad channel 2133mhz ram
4x 256gb ssd
Custom water cooling
and the list goes on and on....