Is My Current 800W PSU Enough?

Hi

I am upgrading my processor ram and motherboard and installing water cooling and was wondering if my current 800W PSU was enough to handle the upgrade.

This will be my specs after the upgrade:

Coolermaster HAF X
Asus Z77 Sabertooth Motherboard
i7 Core 3770k (overclocked to around 4.8 probably) w\ Corsair H100 Liquid Cooling
16GB Corsair Vengeance DDR3 1600 MHz CL9 RAM
AMD 6950 2GB Crossfire X
550GB HDD

The only thing I am carrying over is the crossfire 6950s.

I used the ASUS site to measure the watts needed and it said 900 minimum but I think that is going on the manufacturers safe wattage recommendations, no?

Will it be less than that do you think?

Thanks.