Thanks to everyone for all of the great feedback, here is my base machine on order, I will add Ram, display and external Hdrive (with your advice!):
Mac Pro
AirPort Extreme card (Wi-Fi)
Two 16x SuperDrives
Two 2.8GHz Quad-Core Intel Xeon (8-core)
Apple wireless Mighty Mouse
Apple Wireless Keyboard (English) + Mac OS X
2GB (2 x 1GB)
500GB 7200-rpm Serial ATA 3Gb/s
Accessory kit
NVIDIA GeForce 8800 GT 512MB (Two dual-link DVI)
Mac Pro
AirPort Extreme card (Wi-Fi)
Two 16x SuperDrives
Two 2.8GHz Quad-Core Intel Xeon (8-core)
Apple wireless Mighty Mouse
Apple Wireless Keyboard (English) + Mac OS X
2GB (2 x 1GB)
500GB 7200-rpm Serial ATA 3Gb/s
Accessory kit
NVIDIA GeForce 8800 GT 512MB (Two dual-link DVI)