Power supply help

I have currenty an Antec 850 watt which has been overheating recently and shutting my pc down. my specs are

Asus MB P5N, 2 sticks of DDR2 4 gigs, 3 regular sata drives, 2 optical drives, 5 case fans from 92 to 120mm, Intel E6400 dual core 2 processor, Creative soundblaster pci card, 2 Nvidia Geforce 8800GTS 650mb video cards in sli mode. what do i need to work with this setup properly. thanks

i looked at the calculators it could not be correct that most of them say either 400 watt to 600 watt. not sure what it is .