OWC Accelsior for boot drive -- fastest bootable storage you can get. Obviously if money was no option get the 960GB model.
Fill all 4 drive bays with 4TB storage drives, set them up in RAID 10 to get 8TB of usable, safe storage
Max out the memory and upgrade the CPU to a 3.33 Hex-core (W3680)
Be sad that the ATI 5870 is the best card Apple supports because I don't want to muck with PC cards.